v68k:  Rename byte order functions for generality

Don't let m68k's use of 'word' and 'longword' leak into the generic code
for byte-swapping.
v68k -> iota:  Move endian.hh
iota:  Add 64-bit byte swap functions
Merge branch 'endian'
vfs:  Add posix nodes (stat, lookup, listdir)