ino64 status report 6

[Gleb Kurtsou]

ino64 project aims at extending ino_t to 64 bits and nlink_t to 32 bits
integers providing compatibility shims for both kernel and libc.

I've changed VOP_READDIR implementations for all filesystems in the tree
replacing use of cookies argument with d_off field in struct dirent.
Compatibility layers for linux, svr4 and ibcs2 were also updated. NFS is
not updated yet.

readdir-lint tool was written to test changes.