gcov-tool: Add merge-stream subcommand
gcc/
* doc/gcov-tool.texi: Document merge-stream subcommand.
* doc/invoke.texi (fprofile-info-section): Mention merge-stream
subcommand of gcov-tool.
* gcov-tool.cc (gcov_profile_merge_stream): Declare.
(print_merge_stream_usage_message): New.
(merge_stream_usage): Likewise.
(do_merge_stream): Likewise.
(print_usage): Call print_merge_stream_usage_message().
(main): Call do_merge_stream() to execute merge-stream subcommand.
libgcc/
* libgcov-util.c (consume_stream): New.
(get_target_profiles_for_merge): Likewise.
(gcov_profile_merge_stream): Likewise.