New Addressing Modes implementation.
Update the opcodes for new addressing modes.
Special case the "mixed mode" handling of ASL/LSR/ROL/ROR.

This allows us to pass the test suite but causes the time to run
tests to double and our consing goes up by a factor of 10-20!
Investigate. We get through ~11325 in 12 seconds before this commit,
through 15415 in 20 seconds after.
Fix overflow-p consing madness.
Export reader/writer/getter/setter for Addressing Modes.
Fixup addressing mode tests.