Plus42 Equations, Preview Release

[Thomas Okken]

New update:

1. Made L() invertible again. The example cited by Werner shows that L() is invertible in the HP solver, so it should be in Plus42 as well.
2. Better display size handling across restarts. Also, added GETDS and SETDS functions, for getting and setting the display size programmatically.
3. Now showing WSIZE, SIGNED, and WRAPPED indicators in the header line, while the BASE app or the third row of MODES are active.
4. Now allowing G(X) with undefined X in compatibility mode.
5. While editing equations, the X<>Y, +/-, period, and R/S keys are now relabeled to show the characters you can type with them.
6. L4STK did not fill the stack to 4 levels when used without FUNC. Fixed.