frontend: Add handling for comments

This commit introduces a comment token which is to be ignored by the
parser.

Signed-off-by: Ian Moffett <ian@mirocom.org>

include/frontend/token.h

@@ -19,6 +19,7 @@ typedef enum {
     TT_NAME,        /* [name] */
     TT_NEWLINE,     /* [newline] */
     TT_SHELLBLOCK,  /* [shellblock] */
+    TT_COMMENT,     /* [comment] */
     TT_CC,          /* '.cc' */
     TT_LD,          /* '.ld' */
     TT_COLON,       /* ':' */