Note that address region isolation doesn't prevent explicit label
references from working (add update the test to prove it).
Added a note about pre-label xrefs.
If an address resolves to a user label in an isolated region, we
don't want to use it. However, we still want to try to match it
to a project/platform symbol.
For example, suppose the isolated code wants to reference address
$1C00, which is a memory-mapped I/O location in one area, but a
regular bunch of code in the other. We don't want it to map to
the regular code, but we do want it to resolve to our table of
platform I/O addresses.
We now handle this correctly. The regression test has been updated
to check this. The current implementation does a linear scan through
the symbol table, but I'm hoping this is not a common situation.
The reference manual has been updated to describe the new feature.
This allows regions that hold variable storage to be marked as data
that is initialized by the program before it is used. Previously
the choices were to treat it as bulk data (initialized) or junk
(totally unused), neither of which are correct.
This is functionally equivalent to "junk" as far as source code
generation is concerned (though it doesn't have to be).
For the code/data/junk counter, uninitialized data is counted as
junk, because it technically does not need to be part of the binary.
Move the SourceGen manual to a subdirectory in "docs", so that it can
be accessed directly from the 6502bench web site. The place where
it's installed in the distribution doesn't change.
