man: explain role of uintptr_t & unsigned long in casts from AS pointers

Sparse will warn on casts removing the address space of a pointer
if the destination type is not uintptr_t or unsigned long. But the
special role of these 2 types is not explained in the man page.

So, add an explanation for them in the description of -Waddress-space.

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
1 file changed