warn_summary (subdirectoryFilter): New shell function to optionally filter in/out gcc subdirectories when...

       * warn_summary (subdirectoryFilter): New shell function to
       optionally filter in/out gcc subdirectories when summarizing
       warnings.  Add new flags to support subdirectory filtering.
       Also, ensure the bootstrap stage is a number.  Add some more C
       keywords that are preserved in the "warning type" summary and
       tighten up the "arg ???" regexp.

From-SVN: r22839