userdiff style: re-order drivers in alphabetical order

userdiff style: re-order drivers in alphabetical order

Address some old code smell and move around the built-in userdiff
drivers so they're both in alphabetical order, and now in the same
order they appear in the gitattributes(5) documentation.

The two started drifting in be58e70dba (diff: unify external diff and
funcname parsing code, 2008-10-05), and then even further in
80c49c3de2 (color-words: make regex configurable via attributes,
2009-01-17) when the "cpp" pattern was added.

There are no functional changes here, and as --color-moved will show
only moved existing lines.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>