Fix: ASS "reset style" tag (\r) broke "Position subtitle relative to the video frame".

Fixes #2461.
Update the changelog for a bug fixed in 1219dd2dcbd2b5c3081921f655fc926c6193c470 without being noticed.

Depending on how subtitle entries overlapped, two missing "break" statements could cause some subtitle entries to be added twice to the same segment and thus to be rendered twice. This led to incorrect transparency in the renderer subpicture.

Fixes #2460.
Fix: The last line of the playlist/subtitle files was missing.

CTextFile::ReadString returned false too early, that is as soon as the end-of-line was encountered even if some characters had been read.