Modified "jump to" code to understand address range start/end lines.
If there are multiple starts or ends at the same offset, we jump to
the first one in the set, which is suboptimal but simpler to do.
Simplified the API, embedding GoToMode in the Location object (which
is where it really needs to be, to make fwd/back work right).
Updated HTML export to grey out addresses in NON_ADDR sections.
Changed default pseudo-op strings for address regions to ".addrs" and
".adrend", after trying a bunch of things that were worse. Added
definitions for region-end pseudo-ops to Merlin32 and cc65 for display
on screen.
Added regression test 20260 for address region pre-labels.
Fixed handling of leading underscores in platform/project symbols.
These need to be escaped in 64tass output. Updated regression test
20170-external-symbols to check it.
If you select a local variable, double-click on a reference entry,
and then hit "back", you aren't taken back to the correct place in
the local variable table. This is annoying if you're trying to
explore how a local variable is used.
The NavStack Location object now has a "line delta" that can be
applied to position the selection correctly. This isn't stable
across undo/redo, but it solves the common cases.
This makes LineListGen's "Top" class redundant, so uses of that have
been replaced with Location.
