MFC r340676,r340677,r340679,r340747,r340749,r341682
Implement unr64
pipe: use unr64
tmpfs: use unr64 for inode numbers
uipc_shm: use unr64 for inode numbers
uipc_usrreq: fix inode number assignment
unr64: use locked variant if not LP64
Sponsored by: The FreeBSD Foundation