Plus42 Equations, Preview Release

[Thomas Okken]

New update:

1. In EQN→CALC, fixed the check of whether or not to re-parse the current equation. It needs to be re-parsed if the MODES→STD/COMP setting has changed since the last time it was parsed, but not if the equation contains :STD: or :COMP: tags.

Also, removed a couple of restrictions, of which I can't even remember why I put them in in the first place:

2. Now allowing \(\pi\) as an alternate spelling of PI in both STD and COMP modes. It used to be allowed only in COMP mode for some reason.
3. Now allowing top-level = in equations with parameter lists. That is, PY(A:B:C):A^2+B^2=C^2 was not allowed, while PY:A^2+B^2=C^2 was; now they're both OK.