[PATCH] DocBook: add .gitignore file

when ignoring all DocBook output files git-status output becomes meaningful
again.
Signed-off-by: NMartin Waitz <tali@admingilde.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Documentation/DocBook/.gitignore

+*.xml
+*.ps
+*.pdf
+*.html
+*.9.gz
+*.9