Plus42 Equations, Preview Release

[Thomas Okken]

New update:

1. Fixed crash caused by a bug in CodeMap::lookup(), causing unpleasantness when tracing slightly larger functions.
2. Better handling of where to go when exiting the equation editor.
3. Made the statistics sums, introduced as special variables for equations, into functions callable by user code. They aren't in any catalogs yet, so you have to know what they are called: ΣX, ΣX2, ΣY, ΣY2, ΣXY, ΣN, ΣLNX, ΣLNX2, ΣLNY, ΣLNY2, ΣLNXLNY, ΣXLNY, and ΣYLNX. Apologies about the "ΣN", but calling that one the more logical "N" would just be asking for problems.