Rename PSTL macro's consistent with libstdc++ (and llvm upstream
	project) standards.
	* include/bits/c++config: Rename all macros of the form __PSTL* to
	_PSTL*.
	* include/std/algorithm: Likewise.
	* include/std/execution: Likewise.
	* include/std/numeric: Likewise.
	* include/std/memory: Likewise.
	* include/pstl/glue_memory_impl.h: Likewise.
	* include/pstl/numeric_impl.h: Likewise.
	* include/pstl/glue_memory_defs.h: Likewise.
	* include/pstl/execution_defs.h: Likewise.
	* include/pstl/utils.h: Likewise.
	* include/pstl/algorithm_fwd.h: Likewise.
	* include/pstl/unseq_backend_simd.h: Likewise.
	* include/pstl/glue_execution_defs.h: Likewise.
	* include/pstl/algorithm_impl.h: Likewise.
	* include/pstl/parallel_impl.h: Likewise.
	* include/pstl/memory_impl.h: Likewise.
	* include/pstl/glue_numeric_defs.h: Likewise.
	* include/pstl/parallel_backend_utils.h: Likewise.
	* include/pstl/glue_algorithm_defs.h: Likewise.
	* include/pstl/parallel_backend.h: Likewise.
	* include/pstl/glue_numeric_impl.h: Likewise.
	* include/pstl/parallel_backend_tbb.h: Likewise.
	* include/pstl/numeric_fwd.h: Likewise.
	* include/pstl/glue_algorithm_impl.h: Likewise.
	* include/pstl/execution_impl.h: Likewise.
	* include/pstl/pstl_config.h: Likewise.
	* testsuite/util/pstl/pstl_test_config.h: Likewise.
	* testsuite/util/pstl/test_utils.h: Likewise.
	* testsuite/20_util/specialized_algorithms/pstl/uninitialized_construct.cc:
	Likewise.
	* testsuite/20_util/specialized_algorithms/pstl/uninitialized_copy_move.cc:
	Likewise.
	* testsuite/26_numerics/pstl/numeric_ops/adjacent_difference.cc:
	Likewise.
	* testsuite/26_numerics/pstl/numeric_ops/scan.cc: Likewise.
	* testsuite/26_numerics/pstl/numeric_ops/transform_scan.cc: Likewise.
	* testsuite/26_numerics/pstl/numeric_ops/reduce.cc: Likewise.
	* testsuite/25_algorithms/pstl/alg_nonmodifying/reverse.cc: Likewise.
	* testsuite/25_algorithms/pstl/alg_nonmodifying/nth_element.cc:
	Likewise.
	* testsuite/25_algorithms/pstl/alg_nonmodifying/find_end.cc: Likewise.
	* testsuite/25_algorithms/pstl/alg_nonmodifying/find_if.cc: Likewise.
	* testsuite/25_algorithms/pstl/alg_nonmodifying/none_of.cc: Likewise.
	* testsuite/25_algorithms/pstl/alg_nonmodifying/count.cc: Likewise.
	* testsuite/25_algorithms/pstl/alg_nonmodifying/reverse_copy.cc:
	Likewise.
	* testsuite/25_algorithms/pstl/alg_nonmodifying/equal.cc: Likewise.
	* testsuite/25_algorithms/pstl/alg_nonmodifying/search_n.cc: Likewise.
	* testsuite/25_algorithms/pstl/alg_nonmodifying/find.cc: Likewise.
	* testsuite/25_algorithms/pstl/alg_nonmodifying/all_of.cc: Likewise.
	* testsuite/25_algorithms/pstl/alg_nonmodifying/find_first_of.cc:
	Likewise.
	* testsuite/25_algorithms/pstl/alg_sorting/is_heap.cc: Likewise.
	* testsuite/25_algorithms/pstl/alg_sorting/partial_sort.cc: Likewise.
	* testsuite/25_algorithms/pstl/alg_sorting/partial_sort_copy.cc:
	Likewise.
	* testsuite/25_algorithms/pstl/alg_sorting/lexicographical_compare.cc:
	Likewise.
	* testsuite/25_algorithms/pstl/alg_merge/inplace_merge.cc: Likewise.
	* testsuite/25_algorithms/pstl/alg_merge/merge.cc: Likewise.
	* testsuite/25_algorithms/pstl/alg_modifying_operations/unique_copy_equal.cc:
	Likewise.
	* testsuite/25_algorithms/pstl/alg_modifying_operations/replace_copy.cc:
	Likewise.
	* testsuite/25_algorithms/pstl/alg_modifying_operations/is_partitioned.cc:
	Likewise.
	* testsuite/25_algorithms/pstl/alg_modifying_operations/rotate_copy.cc:
	Likewise.
	* testsuite/25_algorithms/pstl/alg_modifying_operations/remove.cc:
	Likewise.
	* testsuite/25_algorithms/pstl/alg_modifying_operations/copy_if.cc:
	Likewise.
	* testsuite/25_algorithms/pstl/alg_modifying_operations/partition_copy.cc:
	Likewise.
	* testsuite/25_algorithms/pstl/alg_modifying_operations/partition.cc:
	Likewise.
	* testsuite/25_algorithms/pstl/alg_modifying_operations/copy_move.cc:
	Likewise.
	* testsuite/25_algorithms/pstl/alg_modifying_operations/unique.cc:
	Likewise.
	* testsuite/25_algorithms/pstl/alg_modifying_operations/rotate.cc:
	Likewise.
	* testsuite/25_algorithms/pstl/alg_nonmodifying/any_of.cc: Likewise.

	Rename header guards to be consistent with upstream project's
	conventions.
	* include/pstl/glue_memory_impl.h: Rename all macros of the form
	_PSTL_(.*)_H to _PSTL_\U\1_H.
	* include/pstl/numeric_impl.h: Likewise.
	* include/pstl/glue_memory_defs.h: Likewise.
	* include/pstl/execution_defs.h: Likewise.
	* include/pstl/utils.h: Likewise.
	* include/pstl/algorithm_fwd.h: Likewise.
	* include/pstl/unseq_backend_simd.h: Likewise.
	* include/pstl/glue_execution_defs.h: Likewise.
	* include/pstl/algorithm_impl.h: Likewise.
	* include/pstl/parallel_impl.h: Likewise.
	* include/pstl/memory_impl.h: Likewise.
	* include/pstl/glue_numeric_defs.h: Likewise.
	* include/pstl/parallel_backend_utils.h: Likewise.
	* include/pstl/glue_algorithm_defs.h: Likewise.
	* include/pstl/parallel_backend.h: Likewise.
	* include/pstl/glue_numeric_impl.h: Likewise.
	* include/pstl/parallel_backend_tbb.h: Likewise.
	* include/pstl/numeric_fwd.h: Likewise.
	* include/pstl/glue_algorithm_impl.h: Likewise.
	* include/pstl/execution_impl.h: Likewise.
	* include/pstl/pstl_config.h: Likewise.
	* testsuite/util/pstl/pstl_test_config.h: Likewise.

	Synchronize libstdc++ parallel algorithms with upstream
	project.
	* include/pstl/algorithm_fwd.h: Synchronize with
	upstream PSTL project.
	* include/pstl/algorithm_impl.h: Likewise.
	* include/pstl/execution_defs.h: Likewise.
	* include/pstl/execution_impl.h: Likewise.
	* include/pstl/glue_algorithm_impl.h: Likewise.
	* include/pstl/glue_execution_defs.h: Likewise.
	* include/pstl/numeric_fwd.h: Likewise.
	* include/pstl/numeric_impl.h: Likewise.
	* include/pstl/parallel_backend.h: Likewise.
	* include/pstl/pstl_config.h: Likewise.
	* include/pstl/unseq_backend_simd.h: Likewise.
	* include/pstl/parallel_backend_serial.h: New file.
	* include/Makefile.am (pstl_headers): Add
	parallel_backend_serial.h.
	* include/Makefile.in: Regenerate.

	Clean up non-conforming names
	* include/pstl/algorithm_impl.h (__parallel_set_union_op):
	Uglfiy copy_range1 and copy_range2
	(__pattern_walk2_n): Rename local n to __n
	* include/pstl/parallel_backend_tbb.h (struct __binary_no_op):
	Rename parameter _T to _Tp.

	Integrate non-TBB serial backend support
	* include/bits/c++config: Adjust TBB detection logic to select serial
	PSTL backend if no TBB present.
	* testsuite/utils/pstl/test_utils.h: Remove check for
	_PSTL_USE_PAR_POLICIES

From-SVN: r272056