Add .gitignore everywhere based on .cvsignore.

* .gitignore: New.
* build-aux/.gitignore: New.
* data/.gitignore: New.
* doc/.gitignore: New.
* etc/.gitignore: New.
* examples/.gitignore: New.
* examples/calc++/.gitignore: New.
* lib/.gitignore: New.
* m4/.gitignore: New.
* po/.gitignore: New.
* runtime-po/.gitignore: New.
* src/.gitignore: New.
* tests/.gitignore: New.

po/.gitignore

@@ -0,0 +1,22 @@
+/*.gmo
+/*.po
+/*.po~
+/.reference
+/LINGUAS
+/Makefile
+/Makefile.in
+/Makefile.in.in
+/Makevars
+/Makevars.template
+/POTFILES
+/Rules-quot
+/bison.pot
+/boldquot.sed
+/en@boldquot.header
+/en@quot.header
+/insert-header.sed
+/insert-header.sin
+/quot.sed
+/remove-potcdate.sed
+/remove-potcdate.sin
+/stamp-po