warnings: Make WARN_ constants consistent with -w options

Not only does this make it consistent, but allows for automation.

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
diff --git a/asm/parser.c b/asm/parser.c
index dbfb11c..04def6b 100644
--- a/asm/parser.c
+++ b/asm/parser.c
@@ -463,7 +463,7 @@
         if (i == ':') {         /* skip over the optional colon */
             i = stdscan(NULL, &tokval);
         } else if (i == 0) {
-            nasm_warnf(WARN_OL | ERR_PASS1,
+            nasm_warnf(WARN_ORPHAN_LABELS | ERR_PASS1,
                        "label alone on a line without a colon might be in error");
         }
         if (i != TOKEN_INSN || tokval.t_integer != I_EQU) {