TokenizedString duplicates can occur

[markfinal]

Spotted this in BAM v120 (prior to introducing Bam.Core.TokenizedStringArray.ToEnumerableWithoutDuplicates), when compiling the executable in Test13.

When two modules of the same package have the same expression that is based on a package-specific macro, e.g. $(packagedir), then 1) the parsed strings are identical, but 2) the hashes of the individual strings are different, because the modules are different.

Things I have thought about for fixing this:

1. introduce another source of macros, in the PackageDefinition, which defines per-package TokenizedStrings
2. do a pre-pass through macroized TokenizedStrings, in an attempt to turn macro references, e.g. $(packagedir) into a positional argument. If this can happen fully, then the modulewithmacros is no longer needed, and strings ought to have identical hashes after.