Add MRB_API delcaration for mrb_num_div().

[cubicdaiya]

No description provided.

[matz]

Is there any reason for you to use mrb_num_div() from outside of the core (and gems)?

[cubicdaiya]

It might not any reason for use it. But as there is a mismatch between declaration and definition of mrb_num_div(), I think we should make a signature of declaration and definition of mrb_num_div() same.

If mrb_num_div is not assumed to use from outside of the core (and gems),
I think we might apply the following change.

diff --git a/src/numeric.c b/src/numeric.c
index 5cf85fc..da15c92 100644
--- a/src/numeric.c
+++ b/src/numeric.c
@@ -75,7 +75,7 @@ num_pow(mrb_state *mrb, mrb_value x)
  * result.
  */

-MRB_API mrb_value
+mrb_value
 mrb_num_div(mrb_state *mrb, mrb_value x, mrb_value y)
 {
   return mrb_float_value(mrb, mrb_to_flo(mrb, x) / mrb_to_flo(mrb, y));

Or we might remove mrb_num_div() self because mrb_num_div() is not used in mruby now.

[matz]

That way sounds better for me.