bugfix: avoid effect overspeed during transitions (solves #4446)

[softhack007]

this still raises FPS during transitions, but only for effects that normally run very slow (solid).

[blazoncek]

Not a correct solution.
Effect functions need to be modified, there is no way around it.

[DedeHai]

I still don't know why these FX do not run at full speed... I could fix them but have other priorities ATM.
if you want a fixed frame rate without fixed frame-time: I have one possible implementation done in PS 2D Fire FX that also solves transition flickering: the FX renders the frame but does not update any parameters so the frame is identical to the last. maybe some of these FX could do the same or something similar?
I agree that this PR is more of a patch-up than a fix.