Ignore etags, ctags, gtags and cscope.

.gitignore

@@ -265,3 +265,18 @@ Desktop.ini
 $RECYCLE.BIN/
 logo.h
 *.autosave
+
+# https://github.com/github/gitignore/blob/master/Global/Tags.gitignore
+# 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