Feature request: Strict mode

[Malcohol]

Hi!

I was using the basicode-interpreter to develop a BASICODE program. For this use-case it is really handy, but there is a major pitfall: it's very easy to write code which does not satisfy the requirements of correct BASICODE and therefore will not run correctly when loaded into other interpreters.

I propose the addition of an optional strict mode, which issues syntax or runtime errors for non-conformant code.

Examples include the 60 character limit on lines and the variable naming restrictions mentioned in the BASICODE documentation.

Another issue I personally hit is that the interpreter returns the bitwise result for AND and OR. Unfortunately, that behavior should not be relied on in BASICODE, where only logical AND and OR should be assumed. (For example, 2 AND 1 on a ZX Spectrum is 2.)

Thanks again for your awesome work!