* Generally this means removing ref out parameters and instead returning
values. In a couple of cases we will want to avoid copies in future
either by returning const references (e.g. to the pipeline state which
is immutable).
* At the same time, some pointless bool return values that were always
true and didn't indicate errors have been removed. They can be added
again if an error condition comes back.
* Some free functions still have out parameters as C linkage doesn't
allow returning user types by value.
* The C# UI still invokes into C wrappers for all the C++ classes, which
handle taking the return value and doing a copy into an out parameter
still for compatibility.