Suppress warnings of deprecated functions

comment out codes in RBCocoaInstallRubyThreadSchedulerHooks()
with ifdef. this function do not work on 10.6 or later.

git-svn-id: https://svn.code.sf.net/p/rubycocoa/svn/trunk/src@2425 f4f36d40-9719-0410-9868-dde021a23eda
suppress warnings [-Wdeprecated-objc-isa-usage]

- (obj->isa) -> object_getClass(obj)

git-svn-id: https://svn.code.sf.net/p/rubycocoa/svn/trunk/src@2426 f4f36d40-9719-0410-9868-dde021a23eda