Merge pull request #1890 from take-cheeze/fiber_resuming

Revert MRB_FIBER_RESUMED as MRB_FIBER_RESUMING.

include/mruby.h

@@ -70,6 +70,7 @@ typedef struct {
 enum mrb_fiber_state {
   MRB_FIBER_CREATED = 0,
   MRB_FIBER_RUNNING,
+  MRB_FIBER_RESUMING,
   MRB_FIBER_SUSPENDED,
   MRB_FIBER_TERMINATED,
 };