Removed useless yyvals.

src/lex.l

@@ -9,8 +9,8 @@
 \$[a-z0-9._]        { yylval = yytext; return ARG; }        /* Arg of instr */
 ^[a-z.]+            { yylval = yytext; return INSTR; }      /* Instruction */
 \.[^\n]*            { yylval = yytext; return DIRECTIVE; }  /* Assembly */
-\,                  { yylval = yytext; return COMMA; }      /* Comma */
+\,                  { return COMMA; }                       /* Comma */
 #[^\n]*             { yylval = yytext; return COMMENT; }    /* Comment */
-\n                  { yylval = yytext; return NL; }         /* New line */
+\n                  { return NL; }                          /* New line */
 	
 [\s\t]+             { ; }                              /* Ignore whitespace */