Be more POSIXy by using blksize_t (a.k.a. int32) for st_blksize, rather than the current uint32_t.

ok guenther@ deraadt@
split crypt_checkpass off into a new file
One of these optimized stubs creates some incredibly subtle damage,
causing as(1) to create a wrong nop-sled for text segment aligns.
Revert, until it is found and fixed.