Prevent 'mixed declarations and code' C90 warning

src/numeric.c

@@ -207,12 +207,13 @@ flo_to_s(mrb_state *mrb, mrb_value flt)
     char fmt[] = "%." MRB_STRINGIZE(FLO_TO_STR_PREC) "g";
     mrb_value str = mrb_float_to_str(mrb, flt, fmt);
     mrb_int len;
+    char *p;
     char *begp;
+    char *endp;
 
     insert_dot_zero:
     begp = RSTRING_PTR(str);
     len = RSTRING_LEN(str);
-    char *p, *endp;
     for (p = begp, endp = p + len; p < endp; ++p) {
       if (*p == '.') {
         return str;