Add missing undocs

this adds the missing undocumented opcodes to ca65 6502X target, and a little bit of test code.

i have no idea how the changes in src/sim65/main.c made it into this request, they were not commited to this branch at all, ignore that (or just merge it as well =P)
Wouldn't it be desirable to use an unusual "custom" return code here in order to be able to differentiate between a test program returning EXIT_FAILURE and the situation here?