The kernel doesn't have an nlink_t; it just uses the equivalent of
uint32_t. We already had a usable __nlink_t in the C library, so
let's just define our nlink_t in terms of __nlink_t, which is what
__nlink_t was meant for anyway.
Note that our struct stat just follows the kernel, and doesn't refer
to nlink_t anyway.
Change-Id: I2a56e418e42404b1741b08c50554b03c11caebae
2ecc164ae9