cleanup: Kill __[u]int*_t types

Replace them by the stdint [u]int*_t types.
[sandeen: fixes build with musl libc]

Signed-off-by: Felix Janda <felix.janda@posteo.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>