Fixed Mouse Cursor Messages for Win32
The user cursor is only supposed to be set when the mouse is in the client
area of the window, not its border. I resolved it by intercepting the hit
test window message and checking if the mouse is in the client area and
then setting a boolean value which I use in the set cursor message to
determine whether to set the user cursor or delegate to the default window
process. Tested and confirmed working, please merge when ready.
Merge pull request #602 from RobertBColton/master

Fixed Mouse Cursor Messages for Win32