Basic: smarter ALLOC. Keywords. Vector fixes.

Basic: smarter ALLOC. Keywords. Vector fixes.

- Modify ALLOC to take a type (rather than size) and take default
  values to set for the 1-3 values/pointers. Let alloc do the
  ownership taking of the referred values when appropriate.
- Add FORCE_SEQ_TYPE function to coerce sequence to given type. Fixes
  apply and rest on vector. Simplifies concat.
- Use a double ON GOTO structure for calling the native functions in
  DO_FUNCTION.
- Add some stub core functions.
- Move CHECK_FREE_LIST to debug.in.bas
- All changes together save over 1K