Implement "undocumented" 8085 instructions and flags

[hackerb9]

GNUSim8085 should support the "undocumented" 8085 instruction and flags but does not appear to.

It has been known since 1979 that the 8085 contains undocumented opcodes and flag bits. Some clones of the 8085 implement these instructions. Tundra even documented that their CA80C85B supported the undocumented opcodes. (However, whoever wrote the Tundra documentation apparently didn't know how their own chips worked, according to Ken Shirriff, as the flag info is wrong; they simply pasted in the guesses from the 1979 article linked above).

The information on flags from Ken Shirriff and opcodes from Pavel Zima is based on images of the silicon circuitry on the actual chip and are definitively correct.

Besides being interesting, some of the extra features are very handy, for example the K flag (bit 5 of the flag register) which is for comparison between signed values.