The filtering uses the DataGrid View filtering mechanism. The
built-in sorting only operates on a single column, and we really
want a secondary sort on label when the type is used as the key,
so we provide a custom sort method.
If you double-click on the opcode of "JSR label", the code view
selection jumps to the label. This now works for partial operands,
e.g. "LDA #<label".
Some changes to the find-label-offset code affected the cc65 "is it
a forward reference to a direct-page label" logic. The regression
test now correctly identifies an instruction that refers to itself
as not being a forward reference.
The 2014-label-dp test now passes. Prior regression tests are
unaffected.
Also, renamed an IGenerator interface to more accurately reflect
its role.
(issue #37)
