Instead of providing no-op CheckJsr/CheckJsl, plugins now declare
which calls they support by defining interfaces on the plugin class.
I added a CheckBrk call for code like Apple /// SOS calls, which
use BRK as an OS call mechanism. The formatting doesn't work quite
right yet because I've been treating BRK as a two-byte instruction.
Hardly anything else does, and I think it's time I stopped (but not
in this commit).
Note: THIS BREAKS ALL PLUGINS that use the inline JSR/JSL feature,
which is pretty much all of them.
