rust: fix signature of rustlazyancestors_init() function
Obviously, sizeof(int) != mem::size_of::<usize>() on amd64, though the
argument would be passed in 64-bit register anyway.
$ hg init
$ touch unknown
$ touch a
$ hg add a
$ hg ci -m "1"
$ touch b
$ hg add b
$ hg ci -m "2"
Should show unknown
$ hg status
? unknown
$ hg revert -r 0 --all
removing b
Should show unknown and b removed
$ hg status
R b
? unknown
Should show a and unknown
$ ls
a
unknown