mm/memory.c:1944:6: missing binary operator before token "long"

The preprocessor doesn't like the typecast....

PTRS_PER_PGD isn't used in assembly code, so this looks to be safe enough..

This patch helps, but the ia64 build is still broken.  There is no
implementation of __pmd_alloc().

Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>