create po/.gitignore

"dpkg-buildpackage" has a check for untracked files and aborts if there is any.
Therefore add autogenerated files to .gitignore.

Signed-off-by: Benedikt Spranger <b.spranger@linutronix.de>

po/.gitignore

@@ -0,0 +1,11 @@
+Makefile.in.in
+Makevars.template
+Rules-quot
+boldquot.sed
+en@boldquot.header
+en@quot.header
+insert-header.sin
+libuio.pot
+quot.sed
+remove-potcdate.sin
+stamp-po