dtable if the dtable is already installed, otherwise, just add it to
the class's methods list and let
__objc_install_dispatch_table_for_class put it in. Also, change
arguments. All callers updated.
(check_class_methods): New function.
git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/base/trunk@284 72102866-910b-0410-8b05-ffd578937521