[NEW] gettimeofday
v68k-mac:  Store low memory globals as big-endian

While it does mean that the words array will be stored byte-swapped from
a little-endian host's point of view, this simplifies the implementation
considerably.  (This also fixes a failure to byte-swap dynamic variables
like Ticks on read.)
mac:  Add _TickCount trap
[NEW] TickCount