Plus42 Equations, Preview Release

[Thomas Okken]

New update:

1. Parameter count check for calling user code functions, equations stored in variables, and named equations, from equations (XEQ(LBLNAME:​P1:​P2:...), EVALN(VARNAME:​P1:​P2:...), and EQNNAME(P1:​P2:...)). For user code functions without MVAR declarations, the parameters are simply pushed onto the stack, without any further checks, as before.
2. Fixed a few text positioning bugs in the multi-line equation editor.
3. Implemented DIRS, DIR.FCN, UNITS, UNIT.FCN, and EQN functions; these functions jump directly into the DIRS, DIR, UNITS, and UNIT sub-catalogs, and into the equation editor in SOLVER mode, respectively, and their sole reason for existence is so that they can be mapped to keys in the new Plus42 skin.
4. The Plus42 skin was also updated, to make use of those functions. Note that it is rather ugly at the moment, you can tell I haven't made any effort yet to look for fonts that actually match the ones used in the original tyge_nova_P_v2 skin.