Reducing RAM consumption (mainly for Arduino)

[RodionGork]

Arduino has only 2kb of RAM and much is taken up by constant strings etc, because of separate address space for ROM.

Compiler gives 1356 bytes taken before optimization, of them (500 + 150) for basic memory.

[RodionGork]

After switching to compare commands and funcs by hashes 1240.
After moving common messages and errors to progmem 1052.

Basic memory could now be enlarged to (650 + 300).

Code becomes slightly uglier but not much.

[RodionGork]

After replacing "charInStr" inside expr.c it becomes 1036

And after removing arrays of commands and function hashes to switches - 996

Basic memories are enlarged to (700 + 300)