Add printer for current instructions and operands subsets.
Also add basic tests of the Xtensa instructions.
It would be good to check instruction arguments out of order, and invalid register names.
It would be good here to comments marking which instruction formats (RRR, RRI4, RRI8 and so on). re covered, as the difference between them is a common source of bugs. Perhaps next to one of the instructions.
I assume that eventually there will be comprehensive coverage of all the different formats.
Spaces after the commas in this file is inconsistent.
I added more tests for different instruction formats.
Thank you for advice, I've splitted file to several files by commands groups.
Added format information to each instruction.