Win32: Hold a reference to the UserWindow in the web view close callback.
Win32: Hold a reference to the UserWindow in the web view close callback.

This seems to fix segfaults after issuing window.close() on a window
that has just been opened via window.open().

[#301]

wyrover/titanium_desktop,appcelerator/titanium_desktop,appcelerator/titanium_desktop,jvkops/titanium_desktop,appcelerator/titanium_desktop,wyrover/titanium_desktop,wyrover/titanium_desktop,wyrover/titanium_desktop,wyrover/titanium_desktop,wyrover/titanium_desktop,jvkops/titanium_desktop,jvkops/titanium_desktop,appcelerator/titanium_desktop,jvkops/titanium_desktop,jvkops/titanium_desktop,appcelerator/titanium_desktop,jvkops/titanium_desktop