Fix compilation of standalone filters after 3527afd9ec710ab601e25319dddeb482f5001362.

Also move the workaround into its own project.
Always force redraw when the subtitle provider is changed.

There can be cases where the subtitle provider seems to be the same but we need to redraw anyway (e.g. style changes). Since SetSubPicProvider isn't often called, it's not worth making the logic more complex just to save a few redraws.
DVBSub: Fix a stupid parsing bug leading to the wrong page being used.

There is absolutely no reason to copy the region list from the previous page since that means we would just be displaying the old page again instead of the updated one...
DVBSub: Ensure no region is lost to avoid partially rendered subs.

Some regions can be received before they are actually needed. We used to
ignore them but we can need them later so we can't do that.
Update Changelog.txt
DVB and PGS subtitles: Subtitles were sometimes one frame late.

This was invisible most of the time but it could produce blinking in some cases.
DVBSub: "new" throws when memory allocation fails, no need to test against null.

Failure is quite unlikely in those cases and we cannot do much if it ever happens so catching the exception isn't worth it.