Add methods #hash, #eql?, and #== to OSX::ObjCID

Objective-C instances can become key of Hash
even if ObjC to Ruby cache is disabled.

git-svn-id: https://svn.code.sf.net/p/rubycocoa/svn/trunk/src@2489 f4f36d40-9719-0410-9868-dde021a23eda
Remove method "clone" form OSX::ObjCID to disable deep copy

git-svn-id: https://svn.code.sf.net/p/rubycocoa/svn/trunk/src@2490 f4f36d40-9719-0410-9868-dde021a23eda
Fix SEGV at OSX::ObjCID#dup

let to malloc at a function defined by rb_define_alloc_func(),
not initialize.

git-svn-id: https://svn.code.sf.net/p/rubycocoa/svn/trunk/src@2491 f4f36d40-9719-0410-9868-dde021a23eda
Suppress warning return type of init_cls_ObjcID()

git-svn-id: https://svn.code.sf.net/p/rubycocoa/svn/trunk/src@2492 f4f36d40-9719-0410-9868-dde021a23eda