Squashed 'js/thirdparty/jszip/' content from commit bf7ec8c

git-subtree-dir: js/thirdparty/jszip
git-subtree-split: bf7ec8c84bc3c6f486eb576c850dbed562e983a0
Merge commit 'e3aaefcb94e233a3a673312f0aed9cc9dfd078ba' as 'js/thirdparty/jszip'
Another huge pile, resulting in full BASIC support

- Bugs in ADC/SBC's overflow flag, and in BIT
- Slightly modified Kernal to skip memory test
- Game lives alongside BASIC in C000-space
- Oh, and a disasm for VICE-alike stepping output