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.
