Add overlap functionality to gcov-tool.

2014-10-08  Rong Xu  <xur@google.com>

	* gcc/gcov-tool.c (profile_overlap): New driver function
        to compute profile overlap. 
	(print_overlap_usage_message): New.
	(overlap_usage): New.
	(do_overlap): New.
	(print_usage): Add calls to overlap function.
	(main): Ditto.
	* libgcc/libgcov-util.c (read_gcda_file): Fix format.
	(find_match_gcov_info): Ditto.
	(calculate_2_entries): New.
	(compute_one_gcov): Ditto.
	(gcov_info_count_all_cold): Ditto.
	(gcov_info_count_all_zero): Ditto.
	(extract_file_basename): Ditto.
	(get_file_basename): Ditto.
	(set_flag): Ditto.
	(matched_gcov_info): Ditto.
	(calculate_overlap): Ditto.
	(gcov_profile_overlap): Ditto.
	* libgcc/libgcov-driver.c (compute_summary): Make
        it avavilable for external calls.
	* gcc/doc/gcov-tool.texi: Add documentation.

From-SVN: r216015