[NTOSKRNK]

[NTOSKRNK]
Implement ExpWin32SessionCallout, which attaches to the session that the object (desktop or window station) belongs to before invoking any callbacks. The session side of support for this is currently hardcoded to support only a single session. To make this properly work, all callbacks that go through this function have the same function pointer type now, fix this in win32k accordingly.

svn path=/trunk/; revision=61052