Most occurances of U32 were converted to u32. These are cases where
the data represents something that will be written to the hardware.
Other cases were converted to 'unsigned int'.
U32 was the last type in xgi_types.h, so that file is removed.
These two structures were used as the request and reply for certain
ioctls. Having a different type for an ioctl's input and output is
just wierd. In addition, each structure contained fields (e.g., pid)
that had no business being there.
This change requires updates to user-space.
Comment in the code explains it. Basically, I put an if-statement
around a block of code to prevent a NULL pointer dereference that
should never happen in the first place. Eventually, this will need to
come out.