copysym: Integrate code offset into lookup table.

copysym: Integrate code offset into lookup table.

Instead of shifting out a nibble from a 64-bit constant based on the
lookup result, we can just add a byte to each entry in the table with
the same value.  Since we no longer need to worry about fitting the
offsets into 4 bits we can also rearrange the code array a bit, for
an overall code size reduction.