Add a function OSX.objc_classnames()

Retuns all Objective-C classnames.

    OSX.objc_classnames()
    # => ["NSObject", "NSArray", ..]

git-svn-id: https://svn.code.sf.net/p/rubycocoa/svn/trunk/src@2530 f4f36d40-9719-0410-9868-dde021a23eda
Add a function OSX.ns_import_all()

OSX.ns_import_all() invokes ns_import for all Objective-C classes.
OSX.require_frakework invokes ns_import_all implicitly.

this change allows to work the following code on ruby-2.x.

    OSX.require_framework 'MapKit'

    module OSX
        class MKAnnotation
           # extend Objective-C class with in code
        end
    end

RubyCocoa enables this by "osx/objc/oc_import_openclass.rb",
but this feature does not work on ruby-2.x.

git-svn-id: https://svn.code.sf.net/p/rubycocoa/svn/trunk/src@2531 f4f36d40-9719-0410-9868-dde021a23eda