gitignore: Update with new *_gen.c files and generic 'tags'

Change-Id: I6e9df474b4d93e6e20c6d19ac9ffab5b7b959143
diff --git a/.gitignore b/.gitignore
index 2b0ca64..89459f0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -117,9 +117,11 @@
 doc/gsm
 doc/html.tar
 doc/*.tag
+tags
 
 src/crc*gen.c
 src/gsm/gsm0503_conv.c
+src/gsm/*_gen.c
 include/osmocom/core/crc*gen.h
 include/osmocom/core/bit*gen.h
 include/osmocom/gsm/gsm0503.h