glx/windows: Fix compilation with -Werror-format

glx/windows: Fix compilation with -Werror-format

Fix compilation where the DWORD type is used with a format, after
-Werror-format added by c9c1e261.

Some Win32 API types are different fundamental types in the 32-bit and
64-bit versions. This problem is then further compounded by the fact
that whilst both 32-bit Cygwin and 32-bit MinGW use the ILP32 data
model, 64-bit MinGW uses the LLP64 data model, but 64-bit Cygwin uses
the LP64 data model. This makes it near impossible to write printf
format specifiers which are correct for all those targets.

In the Win32 API, DWORD is an unsigned, 32-bit type.  So, it is defined
in terms of an unsigned long, except in the LP64 data model used by
64-bit Cygwin, where it is an unsigned int.

It should always be safe to cast it to unsigned int and use %u or %x.

Reviewed-by: Eric Anholt <eric@anholt.net>