eglplatform: use unsigned long instead of 32-bit ints in generic platform

In the generic Unix case use the "unsigned long" type instead of 32-bit
integers so that the type sizes are consistant on 64-bit machines between X11
and not-X11.

Signed-off-by: Ross Burton <ross.burton@intel.com>
Reviewed-by: Chad Versace <chad.versace@linux.intel.com>
Reviewed-by: Brian Paul <brianp@vmware.com>