Fix PR gcov-profile/46266

	PR gcov-profile/46266
	* lib/gcov.exp: Verify that <built-in>.gcov file is not
	considered.
	* input.h (RESERVED_LOCATION_P): New macro.
	* profile.c (branch_prob): Use RESERVED_LOCATION_P and
	instread of comparison with UNKNOWN_LOCATION.

From-SVN: r240536