Basic: add read-file. Misc basicpp space savings.

Basic: add read-file. Misc basicpp space savings.

- Add read-file which is similar to read-string but from a file name
  rather than a string. This allows steps 0-2 to load although each
  one eventuall crashes with out of memory after evaluating "123"
  a few times.
- basicpp:
    - Renumber the line numbers so they are ordinally increasing. This
      saves 150 or so bytes because GOTO/GOSUB calls have smaller line
      numbers.
    - Shrink 'IF 123' -> 'IF123' for almost 300 byte savings.[:w
    - Simplify PR_MEMORY_SUMMARY output. Save 75 bytes
- Add missing runtest.py change that allows basic tests to pass.