Fix TS2068 ON ERR and add TS2068 DELETE

[ryangray]

Fix bug handling the TS2068 "ON ERR" keyword. It was changing toknum/toklen from ON to ON ERR, causing it to skip handling other ON tokens or tokens in between ON and ONERR, notably RESET. Instead, just skip past "ERR" and stay with token "ON", handling the "ON ERR"/"ONERR" token later.

Added support for the TS2068 DELETE keyword that was overlooked in the TS2068 tokens added in v1.7.0.

I bumped the version to 1.8.6.

[ryangray]

Had to update old Artifact action versions, now checks are passing.

[chris-y]

What's in the massive gap between ON ERR and DELETE?!

[ryangray]

Since DELETE is decimal 12 and there are no other keywords between that and ON ERR, the existing token search mechanism needed to have empties in bewteen. The top of the loop does check for empties to jump to the next one quickly.

We could put a check at the top of the loop just after it decrements toknum for toknum<123 to change it down to 12. After all, the zx81mode does toknum math for RND, INKEY$, and PI since those are far from the main ZX81 tokens. I can change it do do that if you like.

[ryangray]

Okay, made that change. BTW, I'm pretty sure the condition "&& toknum >= 12" (was >= 123) at line 950 is redundant since the token loop condition looks for the NULL at the end of the tokens array.