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

Further trimming mostly for WiPy

Some trimming for WiPy and some changes for the other versions

• Making rarely used small functions inline again, which saves some space. Important for WiPy.
• Catch Ctrl-C on WiPy. Not really nice yet, since the next input byte is lost.
• Tab Size can be set with the Ctrl-A command (if available).
• Simplified Linux main(). No calling options any more.
• Always ask when leaving w/o saving after the content was changed.

WiPy support added and weight reduced

A port for WiPy was added. That caused a re-thinking of the function set. As part of that, I dropped some of the nice-to-haves, to get as many useful functions as possible available on WiPy. Changes:

• Support for WiPy
• Dropped context sensitive behavior of Tab, Backtab, Backspace and Delete
• Left and Right skip over to the next line, if needed
• In the Linux/CPython version window resize triggers Redraw.

GET file added

Just minor changes and bug fixes

• Adding a function GET (Ctrl-O), which inserts the content of a file before the current line
• Both HOME and END stop at start of text is passing by on their way to their destination.
• Flag allowing to replace spaces by Tab when writing the file, opposite to what is done while reading. Tabsize is 8. A tab is inserted whenever possible, even if it replaced a single space character.
• Fixed a mild amnesia in UNDO

UNDO added

Added a multilevel UNDO (Ctrl-Z) for most functions that change the content. Other changes:

• Backspace at the first non-blank character mimics BackTab, if Auto-indent is enabled
• Added a REDRAW (Ctrl-E) function, which checks for the changed screen size after the window size has been changed.
• Added a line number column on the left side of the screen (can be turned off).
• Improved the scrolling speed, such that it lags less.
• Some code simplification and straightening, such that functions group better and a easier to understand.

Mouse support added

A few minor changes:

• Simple Mouse support for scrolling and placing the cursor
• Flags setting for search case, autoindent on/off and statusline on/off
• goto line sets cursor to the middle row
• function pye(..) returns a value now

Simplified Keyboard Mapping

Removed the duplicated definitions for cursor motion keys. Allowed both \r and \n for ENTER, and both \x08 and \x7f for BACKSPACE, which avoid some hazzle with terminal settings. Removed auto-indent from the minimal version.

A good balance of size and functions

v1.0

Some hopefully better explanations; fixed typos and errors