Revert "git-notify: Ignore `empty' commits"

Revert "git-notify: Ignore `empty' commits"

This reverts commit db63fbfa036f5cd757aedf4547fef9e195a8c285, as it is
no longer needed and we'd like to keep the diff against the git-notify
version maintained by the Wine people as small as possible.  The purpose
of db63fbfa was to suppress notifications on empty merge commits, which
can now be requested directly by specifying git-notify's "-X" option.
(Our change was implemented before the "-X" option was available, even
though the Git history suggests otherwise.)

Conflicts:

	tools/git-notify