warn_summary (longLineFilter): New shell function to encapsulate this functionality.

        * warn_summary (longLineFilter): New shell function to encapsulate
        this functionality.  It is off by default, only active if -llf
        flag is specified.
        (subdirectoryFilter): Fix bug in filtering which made some
        subdirectory warnings erroneously appear in the toplevel set.
        (stageNfilter): Renamed from `stageNwarns'.  Updated to collect
        warnings from stage1 as well as stage0, which means warnings from
        outside the bootstrap directory.  Eg, the libraries, etc.
        (warningFilter): New shell function to encapsulate this
        functionality.
        (keywordFilter): New shell function to encapsulate this
        functionality.
        Store data in a temp file rather than calculating it 3x.  Arrange
        to remove it on exit and signals.
        Add -pass/-wpass flags to do "pass through" (i.e. manual
        inspection) of bootstrap output from a particular stageN as well
        as language subdirs.
        Add better comments/documentation.

From-SVN: r23473