vm.c: partially revert r60558

because it was actually used in
https://github.com/tmm1/rbtrace/blob/v0.4.8/ext/rbtrace.c#L329
and deprecated in r60579 AFTER removal in r60558.

ko1 agreed that we should keep just deprecated in Ruby 2.5 and remove it
later, and I'm commiting this because I want to make rbtrace.gem
installation successful.

backward.h: modify r60579 to make rb_frame_method_id_and_class()
compilable.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60964 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

include/ruby/backward.h

@@ -50,7 +50,7 @@ DECLARE_DEPRECATED_INTERNAL_FEATURE(rb_struct_ptr);
 DECLARE_DEPRECATED_INTERNAL_FEATURE(rb_generic_ivar_table);
 
 /* vm.c */
-DECLARE_DEPRECATED_INTERNAL_FEATURE(rb_frame_method_id_and_class);
+DEPRECATED(int rb_frame_method_id_and_class(ID *idp, VALUE *klassp));
 
 /* from version.c */
 #ifndef RUBY_SHOW_COPYRIGHT_TO_DIE

vm.c

@@ -2048,6 +2048,12 @@ rb_ec_frame_method_id_and_class(const rb_execution_context_t *ec, ID *idp, ID *c
     return rb_vm_control_frame_id_and_class(ec->cfp, idp, called_idp, klassp);
 }
 
+int
+rb_frame_method_id_and_class(ID *idp, VALUE *klassp)
+{
+    return rb_ec_frame_method_id_and_class(GET_EC(), idp, 0, klassp);
+}
+
 VALUE
 rb_vm_call_cfunc(VALUE recv, VALUE (*func)(VALUE), VALUE arg,
 		 VALUE block_handler, VALUE filename)