complex.c: use `mrb_num_div_flo` to avoid copying function.

This change relies that `mrb_num_div_flo` does not use `mrb` inside.

mrbgems/mruby-complex/src/complex.c

@@ -235,19 +235,10 @@ complex_mul(mrb_state *mrb, mrb_value x)
   }
 }
 
-mrb_float
-div_flo(mrb_float x, mrb_float y)
-{
-  if (y != 0.0) {
-    return x / y;
-  }
-  else if (x == 0.0) {
-    return NAN;
-  }
-  else {
-    return x * (signbit(y) ? -1.0 : 1.0) * INFINITY;
-  }
-}
+#ifndef MRB_NO_FLOAT
+mrb_float mrb_num_div_flo(mrb_state*, mrb_float, mrb_float);
+#define div_flo(x,y) mrb_num_div_flo(NULL, x, y)
+#endif
 
 /* Arithmetic on (significand, exponent) pairs avoids premature overflow in
    complex division */
@@ -341,8 +332,6 @@ complex_div(mrb_state *mrb, mrb_value self)
   return complex_new(mrb, F(ldexp)(zr.s, zr.x), F(ldexp)(zi.s, zi.x));
 }
 
-mrb_float mrb_num_div_flo(mrb_state*, mrb_float, mrb_float);
-
 #ifndef MRB_USE_RATIONAL
 mrb_int mrb_num_div_int(mrb_state *mrb, mrb_int x, mrb_int y);
 
@@ -365,7 +354,7 @@ int_div(mrb_state *mrb, mrb_value x)
     x = complex_new(mrb, (mrb_float)a, 0);
     return mrb_funcall_id(mrb, x, MRB_OPSYM(div), 1, y);
   default:
-    return mrb_float_value(mrb, div_flo(mrb, (mrb_float)a, mrb_to_flo(mrb, y)));
+    return mrb_float_value(mrb, div_flo((mrb_float)a, mrb_to_flo(mrb, y)));
   }
 }
 
@@ -385,7 +374,7 @@ int_quo(mrb_state *mrb, mrb_value x)
     x = complex_new(mrb, (mrb_float)a, 0);
     return mrb_funcall_id(mrb, x, MRB_OPSYM(div), 1, y);
   default:
-    return mrb_float_value(mrb, mrb_num_div_flo(mrb, (mrb_float)a, mrb_to_flo(mrb, y)));
+    return mrb_float_value(mrb, div_flo((mrb_float)a, mrb_to_flo(mrb, y)));
   }
 }
 #endif