Smart relaxation of TOP N counter.

Smart relaxation of TOP N counter.

	PR tree-optimization/92924
	* profile.c (compute_value_histograms): Divide
	all counter values.
	PR tree-optimization/92924
	* libgcov-driver.c (prune_topn_counter): New.
	(prune_counters): Likewise.
	(dump_one_gcov): Prune a run-time counter.
	* libgcov-profiler.c (__gcov_topn_values_profiler_body):
	For a known value, add GCOV_TOPN_VALUES to value.
	Otherwise, decrement all counters by one.