(15C) Decoder for HP 15c programs

[pinkman]

New version attached:
- fixed the lack of .0 to .9 decoding
- used the unicode chars given by Dieter, except for the square root (SQRT) and the standard deviation (SDEV) to increase readability
- given the same privileges to comma and decimal point, whatever the above discussion may have conclude or not (I'm in a "comma zone" but with computers I prefer using the decimal point to avoid confusion in source code)