PR gcov-profile/78086
	* g++.dg/gcov/pr16855.C: Clean up the test case.
	* g++.dg/gcov/pr16855-priority.C: New test.
	* coverage.c (build_init_ctor): Don't use priority {cd}tors if
	not supported by a target.  Set priority to 100 if possible.
	(build_gcov_exit_decl): Likewise.

From-SVN: r242877