Fix compiler errors from MRB_NO_FLOAT; #5185

Also added `no-float.rb` target in `build_config`.

src/codedump.c

@@ -141,7 +141,9 @@ codedump(mrb_state *mrb, const mrb_irep *irep)
     op_loadl:
       switch (irep->pool[b].tt) {
       case IREP_TT_FLOAT:
+#ifndef MRB_NO_FLOAT
         printf("OP_LOADL\tR%d\tL(%d)\t; %f", a, b, (double)irep->pool[b].u.f);
+#endif
         break;
       case IREP_TT_INT32:
         printf("OP_LOADL\tR%d\tL(%d)\t; %" PRId32, a, b, irep->pool[b].u.i32);