Further support for WiPy
WiPy fixes and other minor changes
- Fixed a memory leak in REDRAW, removed every instance of "del name"
- Changed REDRAW to tell the amount of free memory
- changed wr() for WiPy
- Simplified the internal interface to init_tty()
- Changed the handling of reading an empty file
- Non-supported functions in the minimal version like REPLACE trigger a "Sorry" message
- Try to recover from MemoryError by clearing the line-buffer and UNDO