MINOR: Configure the `cpp` userdiff driver for *.[ch] in .gitattributes

This might improve the output of `git diff` in certain cases. Especially
`git diff --word-diff` will be much more useful.

Does not affect the generated code, may be backported for consistency if
desired.

(cherry picked from commit 6bcdc6530a437bb4eca24fb41439e34690376972)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
1 file changed