Name mangle labels based on Forth names to work with the assembler.
Emit word names in target output propery.

- Reverse names, set bit 7 in last character and pad with 0 if needed.
- Language.Forth.CodeGenerate now knows about directives, it just asks
  for a wrapper function to make an instruction (which is reality will be
  the data contructor for wrapping directives).
  It will now use both .byte and .ascii directives.