Collect Character restarts
|RST_4||0020||Collect Next character|
RST 3 returns the character addressed by
CHADD returning it if it's printable.
If it is not printable then
CHADD is incremented until a printable character is found.
RST 4 increments
CHADD first before returning the next printable character.
These two resets are used in multiple places in the ROM, the BASIC tokenizer being one of them.