Add intermediate build products to .gitignore

Temporaries such as configure.ac+ and Documentation/*.xml+
sometimes remain after an interrupted build.  Tell git not to
track them.

Signed-off-by: Jonathan Nieder <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: jrn

.gitignore

@@ -168,6 +168,7 @@ git.spec
 *.exe
 *.[aos]
 *.py[co]
+*+
 config.mak
 autom4te.cache
 config.cache