This PR changes the `swap_handles` variable of the
`BeztMap` from `short` to `bool`.
The only reason it was a `short` was so that 0 could be
interpreted as "not checked" within the sorting loop.
Instead, I moved the checking for swapping to a separate loop.
That means the `BeztMap` array needs to be traversed one more time,
but given sorting might already do that multiple times that won't be
a performance issue
(plus we don't have the `if` within the sorting loop potentially messing up branch prediction).
In addition to that this PR also removes `prev_ipo` and
`current_ipo` from the `BeztMap` struct. Those were never used.
This is also partly a fix to restore 3.6 behavior.
With the move to C++, `swap_handles` was never initalized,
so the logic ` if (bezm->swap_handles == 0)` would always be false.
That resulted in the following behavior when
**rotating a bunch of keys 180deg** around their common center.
Pull Request: https://projects.blender.org/blender/blender/pulls/121076
c464426475