* macro.c (_cpp_builtin_macro_text): Handle BT_COUNTER.
	* pch.c (cpp_write_pch_deps): Save __COUNTER__ state.
	(cpp_write_pch_state): Save __COUNTER__ state.
	(cpp_valid_state): Check valid __COUNTER__ state.
	(cpp_read_state): Read new __COUNTER__ state.
	* include/cpplib.h (enum builtin_type): Add BT_COUNTER enumerator.
	* init.c (builtin_array): Add __COUNTER__/BT_COUNTER.
	* internal.h (struct cpp_reader): Add counter member.

	* gcc.dg/cpp/counter-1.c: New test.
	* gcc.dg/pch/counter-1.c: New test.
	* gcc.dg/pch/counter-1.hs: New file.
	* gcc.dg/pch/counter-2.c: New test.
	* gcc.dg/pch/counter-2.hs: New file.
	* gcc.dg/pch/counter-3.c: New test.
	* gcc.dg/pch/counter-3.hs: New file.

	* doc/cpp.texi (Common Predefined Macros): Add __COUNTER__
	description.

From-SVN: r125041