Ignores for gtags and cscope added.

Global/Tags.gitignore

@@ -1,5 +1,14 @@
-# Ignore tags created by etags and ctags
+# Ignore tags created by etags, ctags, gtags (GNU global) and cscope
 TAGS
 !TAGS/
 tags
 !tags/
+gtags.files
+GTAGS
+GRTAGS
+GPATH
+cscope.files
+cscope.out
+cscope.in.out
+cscope.po.out
+