git-gui: Include 'war on whitespace' fixes from git.git

git-gui: Include 'war on whitespace' fixes from git.git

Earlier git.git applied a large "war on whitespace" patch that was
created using 'apply --whitespace=strip'.  Unfortunately a few of
git-gui's own files got caught in the mix and were also cleaned up.
That was a6080a0a44d5ead84db3dabbbc80e82df838533d.

This patch is needed in git-gui.git to reapply those exact same
changes here, otherwise our version generator script is unable to
obtain our version number from git-describe when we are hosted in
the git.git repository.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>