Log Message:
Update grepmail to 5.00

Changes:

- grepmail is now orders of magnitude faster for mailboxes which have very
  large (>30MB) emails in them
- "grep" is now used to find the start of emails, if it is installed. For
  mailboxes with large emails in them, this can speed things up by about 5x.
- Reduced memory consumption by about 3 times.
- -- now marks the end of options and the beginning of folders (Thanks to
  Reuben Thomas <rrt@sc3d.org> for the idea.)
- -f now reads patterns from a file like GNU grep does. (Feature suggestion by
  Darxus@chaosreigns.com)
- Added smail compatibility. (Thanks to Roy <qroy@ghg.net> for the patch.)
- The "**" prefix on warnings has been changed to "grepmail:"
- Date specifications without times (e.g. "today") are interpreted as \ 
midnight
  of the given day instead of the current time of that day. (Bugfix and
  initial patch by Reuben Thomas <rrt@sc3d.org>.)
- Fixed -i when used with -Y--it was always case sensitive. (Bugfix by Michael
  C. Toren <mct@toren.net>)
- Updated t/functionality.t to avoid running gzip-related test cases when gzip
  is not installed on the system.
- Improved some error messages so that they prepend "grepmail: " as they
  should
- Cleaned up some warnings about ambiguous hash values (Thanks to Philip
  Douglass <philipsd@sf.net> for pointing them out in a bug report.)
- Added a warning about the version of perl required for new pattern features
  (Thanks to Philip Douglass <philipsd@sf.net> for the bug report.)
- -t flag is now -j
- Fixed broken Gnus support
- Improved test case for Gnus