MINOR: lua: typo in an error message

A small typo was introduced in an error message, occuring when too many
arguments are provided ("Malformed argument mask").
diff --git a/src/hlua.c b/src/hlua.c
index a0e4d91..9ded473 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -420,7 +420,7 @@
 
 		/* Check oversize. */
 		if (idx >= ARGM_NBARGS && argp[idx].type != ARGT_STOP) {
-			WILL_LJMP(luaL_argerror(L, first + idx, "Malformad argument mask"));
+			WILL_LJMP(luaL_argerror(L, first + idx, "Malformed argument mask"));
 		}
 
 		/* Check for mandatory arguments. */