DWIM for _ and left-arrow (and clisp ) #2302
Description
This idea is to make the cases where a source file has a underbar in a CLISP expression where it should be a left-rrow (like a create expression) to dwim it into a left-arrow. more ambitious would be to choose an alternate non-ascii character for : for CLISP of record expressions. I think these changes might make CLISP useful, again. (I don't think there are lisp source uses of ^ or uparrow -- are there?).
Awhile ago I did a grep scan of all the source files, looking for all occurrences of the arrows, carets, underscores and non-Ascii characters. There are very few carets, basically in clisp/dwim, where they are clearly intended to be uparrows. And almost all (if not all) underscores are in clisp and create expressions that again are intended to be uparrows.
So I think it is safe to assume that our source files already default to MCCS, even though we have thought of them as XCCS (or XCCS$, to be more accurate). They show up the way you would expect (modulo the characters that are outside of 7-bit ascii, which are already [X|M]CCS) if your fontprofile uses Gacha/Helvetica/Timesroman instead of Terminal/Modern/Classic. If the NS fonts are flipped, you would see the same images for both sets of fonts.
(BTW, the scan was a lot harder because so many files were not prettyprinted and line-broken in meaningful ways)