Fix rb_struct_members and rb_struct_s_members

Author: eregon

spec/tags/optional/capi/struct_tags.txt

@@ -1,4 +1,2 @@
 fails:C-API Struct function rb_struct_getmember returns the value of a struct member
 fails:C-API Struct function rb_struct_getmember raises a NameError if the struct member does not exist
-fails:C-API Struct function rb_struct_s_members returns the struct members as an array of symbols
-fails:C-API Struct function rb_struct_members returns the struct members as an array of symbols

src/main/c/cext/struct.c

@@ -65,11 +65,11 @@ VALUE rb_struct_new(VALUE klass, ...) {
 }
 
 VALUE rb_struct_s_members(VALUE klass) {
-  return RUBY_INVOKE(klass, "rb_struct_s_members");
+  return RUBY_INVOKE(klass, "members");
 }
 
 VALUE rb_struct_members(VALUE s) {
-  return RUBY_INVOKE(s, "rb_struct_members");
+  return RUBY_INVOKE(s, "members");
 }
 
 VALUE rb_struct_size(VALUE s) {