rdesktop seamless integration crashes on 64bit

Binary package hint: rdesktop

Using rdesktop on an AMD64 bit architecutre with the seamlessRDP feature
http://www.cendio.com/seamlessrdp/
crashes rdesktop whenever a new window is opened.

I've traces this back to some odd definition in the Xorg spec, where 32 bit values
are specified as long, regardless of architecture, and hence need to be 64 bit on
AMD64. The original code uses uint32_t, which causes crashes during parsing of
icons for an enhanced window manager hint.

The attached patch fixes the issue, and adds sanity checks to catch similar errors
during pointer arithmetic on icon data. The upstream ML seems to be dead, hence
the repost here, with the hope that Ubuntu integrates the patch.

The patch has been in heavy usage on my machine, and no furhter crashes occured.