o Makes the tab key intelligently insert spaces when appropriate (see Help
list banter twixt David Ascher and me; idea stolen from every other editor
on earth <wink>).

o newline_and_indent_event trims trailing whitespace on the old line (pymode
and Codewright).

o newline_and_indent_event no longer fooled by trailing whitespace or
comment after ":" (pymode, PTUI).

o newline_and_indent_event now reduces the new line's indentation after
return, break, continue, raise and pass stmts (pymode).

The last two are easy to fool in the presence of strings & continuations,
but pymode requires Emacs's high-powered C parsing functions to avoid that
in finite time.