Avoid warning for M_RET_ARG if there is the exact number of argument.

Add internal M_TRIPLE_* macros (TBC)

m-core.h

@@ -809,7 +809,7 @@ M_BEGIN_PROTECTED_CODE
    Generated by:
    for i in $(seq 1 53 ) ; do printf "#define M_RETI_ARG%d(" $i; for j in $(seq 1 $i) ; do printf "_%d, " $j ; done ; printf "...) _%d\n#define M_RET_ARG%d(...) M_RETI_ARG%d(__VA_ARGS__,)\n\n" $i $i $i ; done
   */
-#define M_RET_ARG(n, ...)  M_C(M_RET_ARG, n)(__VA_ARGS__)
+#define M_RET_ARG(n, ...)  M_C(M_RET_ARG, n)(__VA_ARGS__, )
 
 #define M_RETI_ARG1(_1, ...) _1
 #define M_RET_ARG1(...) M_RETI_ARG1(__VA_ARGS__,)
@@ -1053,6 +1053,10 @@ M_BEGIN_PROTECTED_CODE
 #define M_PAIR_1(a,b) a
 #define M_PAIR_2(a,b) b
 
+/* Same for triple */
+#define M_TRIPLE_1(a,b,c) a
+#define M_TRIPLE_2(a,b,c) b
+#define M_TRIPLE_3(a,b,c) c
 
 /* Skip the Nth first arguments of a VA_ARGS
    Generated by: