Early data sheets listed BRK as one byte, but RTI after a BRK skips
the following byte, effectively making BRK a 2-byte instruction.
Sometimes, such as when diassembling Apple /// SOS code, it's handy
to treat it that way explicitly.
This change makes two-byte BRKs optional, controlled by a checkbox
in the project settings. In the system definitions it defaults to
true for Apple ///, false for all others.
ACME doesn't allow BRK to have an arg, and cc65 only allows it for
65816 code (?), so it's emitted as a hex blob for those assemblers.
Anyone wishing to target those assemblers should stick to 1-byte mode.
Extension scripts have to switch between formatting one byte of
inline data and formatting an instruction with a one-byte operand.
A helper function has been added to the plugin Util class.
To get some regression test coverage, 2022-extension-scripts has
been configured to use two-byte BRK.
Also, added/corrected some SOS constants.
See also issue #44.
