"SWAP" statement fixed

[Charlie Veniot]

BASIC Anywhere Machine has a copy of wwwBASIC.js directly embedded in the TiddlyWiki, so at this point we can say that I've created a fork of the wwwBASIC.js source code.

The wwwbasic github project has been dormant for the last few years, and I don't feel comfortable mucking about with either github or the wwwbasic project, so I'm just going to maintain my version of wwwbasic, taking note of my changes/additions and suggesting those via issues on the project's github page.

The bug with the "SWAP" statement in wwwbasic.js:

SWAP A$, B$

results in

• A$ getting set to the value of B$
• B$ getting set to the new value of A$ (i.e. B$ doesn't change at all).

BASIC Anywhere Machine fixes that, so the values of the variables are properly swapped.