generator.cs: generate partial EventArgs classes

Allows notification EventArgs to be augmented.
generator: support [Internal] in EventArgs classes
Rename internally used selector to not match an internal Apple selector.

Support case #29200 a customer got a warning about the non-public selector
'apply' when submitting to the app store. Rename our selector so that it
doesn't clash with whatever Apple's doing.
Manually bind two .ctor to ensure their native/managed signatures match
Process .ctor too - merged pull request #47 from Stephane Delcroix
provide log progress, fix a typo (modified pull request #48 from Stephane Delcroix
Fix MonoMac/MonoTouch (for MonoMac builds)
CoreAnimation: start fixing the return value for CAKeyFrameAnimation.FromKeyPath

We should have made this method return a CAKeyFrameAnimation, instead it returns
the base class.   So we now show an Obsolete, pointing developers to the new name
and one day we will be able to change the return type.

We need this two-step process, because changing the return value could potentially
break source code compilation (even if the method has always returned a
CAKeyFrameAnimation), some users might have:

CAPropertyAnimation prop = CAKeyFrameAnimation.FromKeyPath (...);