Proposed fix for issue 200 - improper handling of mouseEntered when the view does not override it

[Saikat Chakrabarti]

http://github.com/280north/cappuccino/issues/#issue/200 is the
original issue. I have a proposed fix at
http://github.com/saikat/cappuccino/commit/8a2788f7ad4d9a2423a004f8b991bf42e3588efe
. I'm fairly unsure about this fix (I just made mouseEntered and
mouseExited not go down the responder chain) because the documentation
for NSResponder says "The default implementation simply passes this
message to the next responder." (
http://developer.apple.com/documentation/Cocoa/Reference/ApplicationKit/Classes/NSResponder_Class/Reference/Reference.html#//apple_ref/occ/instm/NSResponder/mouseEntered:
). However, i just tested out a Cocoa app where I had a view that did
not implement mouseEntered as a subview on a view that did implement
mouseEntered (a NSTextField on top of a custom view), and hovering
over the view that did not implement mouseEntered did not make an
extra call to mouseEntered on the superview.