Mips16 constant islands port of ARM passing test-suite now

There are still two more patches to put back for conditional branches but the main part of the constant islands
as well as unconditional branches seems to work fine and has all been pushed upstream. The rest should be pushed
next week.

At least it passes all of test-suite.

I'm not ready to turn it on as a default for now because I need to review it a lot and do some more testing and cleanup.

I kept it mostly 95% as is from the ARM version but I deleted a lot of the alignment stuff (known bits, pre and post alignment bits, etc). I think that that stuff is mostly
a bandaid for not expanding the inline assembler and the better way to solve all those related issues is to really
parse the inline assembler or else to go a pessimistic mode in the presence of inline assembler.

So I think that it would be easy to make a target independent version based on the mips port.
By comparing it to the ARM version, it would be clear how to parameterize it. Not volunteering though to do this. :frowning:
I have no spare cycles.