tkutil.c: prevent temporary objects from GC
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41351 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
tkutil.c: prevent temporary objects from GC
rb_intern_str() instead of rb_intern() and RSTRING_PTR() with
RB_GC_GUARD(), to prevent temporary objects from GC.
[ruby-core:39000] [Bug #5199]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41351 b2dd03c8-39d4-4d8f-98ff-823fe69b080e