build: Add .gitignore files to EXTRA_DIST.

As a packager, I want to be able to do "git format-patch
v3.0..origin/master" and I want the generated patches to apply cleanly
against the 3.0 tarball. The patches don't currently apply cleanly if
there are any changes to the .gitignore files, because the .gitignore
files are not shipped in the tarball. This patch fixes that problem.

Makefile.am

@@ -31,7 +31,15 @@ EXTRA_DIST = \
 	vala/libpulse.deps \
 	vala/libpulse.vapi \
 	vala/libpulse-mainloop-glib.deps \
-	vala/libpulse-mainloop-glib.vapi
+	vala/libpulse-mainloop-glib.vapi \
+	.gitignore \
+	doxygen/.gitignore \
+	m4/.gitignore \
+	man/.gitignore \
+	po/.gitignore \
+	src/.gitignore \
+	src/daemon/.gitignore \
+	src/pulse/.gitignore
 
 SUBDIRS = src doxygen man po