This implements all the ranges members defined in [specialized.algorithms]:

  ranges::uninitialized_default_construct
  ranges::uninitialized_value_construct
  ranges::uninitialized_copy
  ranges::uninitialized_copy_n
  ranges::uninitialized_move
  ranges::uninitialized_move_n
  ranges::uninitialized_fill
  ranges::uninitialized_fill_n
  ranges::construct_at
  ranges::destroy_at
  ranges::destroy

It also implements (hopefully correctly) the "obvious" optimizations for these
algos, namely that if the output range has a trivial value type and if the
appropriate operation won't throw then we can dispatch to the standard ranges
version of the algorithm which will then potentially enable further
optimizations.

libstdc++-v3/ChangeLog:

	* include/Makefile.am: Add <bits/ranges_uninitialized.h>.
	* include/Makefile.in: Regenerate.
	* include/bits/ranges_uninitialized.h: New header.
	* include/std/memory: Include it.
	* testsuite/20_util/specialized_algorithms/destroy/constrained.cc: New
	test.
	* .../uninitialized_copy/constrained.cc: New test.
	* .../uninitialized_default_construct/constrained.cc: New test.
	* .../uninitialized_fill/constrained.cc: New test.
	* .../uninitialized_move/constrained.cc: New test.
	* .../uninitialized_value_construct/constrained.cc: New test.