Remove mterp "alternate" opcode handlers.

They are currently unused and I don't have plans to use them.

The alternate table made it possible to enable extra mterp checks.
However, it is possible to move the debug checks to the main path.

Test: test.py -b -r --interpreter -t 001-HelloWorld
Change-Id: I45a39ec73abaefaecf5b8c636f3f9d519a0a8bb0