FFVCL Encoder 7.4 and Player 7.4 Released

2019.09.01 FFVCL Encoder & Player 7.4

[Common]
* update to FFmpeg 4.2
* support macOS 64-bit [Delphi 10.3.2, FFVCL Professional]

[DLLs]
* FFmpeg DLLs built base on official ffmpeg 4.2
* This version NOT compatible with previous FFmpeg DLLs.