String op improvements

[patricksurry]

Saves about 50 bytes overall. Simplifies CLEAVE (faster, smaller and avoids input manipulation). Shortens -LEADING/TRAILING: this slows it down a little after removing some inlining, but also because I switched to the shared jsr is_whitespace instead of the specific cmp #AscSP. I'm not sure if that was intentional but seemed like it should be symmetric with LEADING and CLEAVE?

The overall test cycles increase somewhat because -TRAILING is used in various tests, but I imagine in practice the CLEAVE improvement might be more important? Equally I could just undo the -TRAILING changes.

Cycle counts with simple test:

word	before	after
s" a b c " CLEAVE	1225	487
s" txt " -LEADING	354	234
s" txt " -TRAILING	224	430*

*337 with cmp #AscSp instead of jsr is_whitespace.

[patricksurry]

this inline slows down the loop; could undo

[patricksurry]

this also slows it down, but seems better than just cmp #' ' unless that was intentionally avoiding other whitespace?

[SamCoVT]

One of the differences is that -TRAILING is an ANS standard word, while the others are Tali specific. The standard specifically mentions spaces, which are elsewhare defined as BL and the value 0x20.
https://forth-standard.org/standard/string/MinusTRAILING

[patricksurry]

ah, that makes sense. so I'll switch -TRAILING back to only check for spaces. Does it make sense for -LEADING to behave in a similar same (only strip spaces specifcally) or should it continue to strip other whitespace as well?

[SamCoVT]

I agree that -TRAILING should use only spaces, but I'm fine with the other words skipping any whitespace and I think your changes look fine for those words.