Check that we don't overrun the end of the property data while converting icons
See http://cygwin.com/ml/cygwin-xfree/2013-06/msg00040.html for testcase.
Also, some warning fixes in winXIconToHICON()
Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk>
Reviewed-by: Colin Harrison <colin.harrison@virgin.net>