Fill in all the documentation

This is really just a first pass through the documentation, but at
least it's all written now.  Hopefully it makes some form of sense...
Fix some label/ref pairs

I didn't actually read anything for this, I just went through and
searched for ??.  At least it's something!
Clean up a suprious newline
Fix an unused variable

This was found with scan-build, but was harmless.
Fix a memory leak in pbashc

This was found using scan-build.
Bump version to 0.7.3