Replace STAUTOPLAY with a simple flag

[twopointzero]

Can you write a one-sentence description of your request?
Replace STAUTOPLAY with a simple flag.

What is the current behavior?
STAUTOPLAY is a structure of many members, each representing various parts of instruments no longer supported by the software. The code (that matters) always sets all of its values true or false, usually via a loop, and then the structure gets passed around and processed by indexing into its content over and over.

What is the expected behavior?
Especially with the removal of viewer support, this structure and all code processing it can be replaced with the management of a simple boolean and, as it just so happens, the code that cares was already having to manage another autoplay-related boolean for that anyway, so those can almost surely be merged.

What is the motivation / use case for changing the behavior?
Code complexity, maintainability, the usual. :)