GPL update for FFmpeg v3.4.x.

Features

• New external libraries supported: expat, libilbc, opus and snappy
• Support for GPL libraries; x264 and Xvid added
• fontconfig dependency changed from libxml2 to expat
• Assembly enabled for gmp library on Android and IOS x86, x86-64 architectures
• Better ASMFLAGS support for ios.sh
• --reconf-LIBRARY option enhanced to call autoreconf with different arguments
• --rebuild-LIBRARY option implemented
• Default values (enabled/disabled) of all build options added in top level build scripts
• Built-in IOS support added for bzip2, Core Image and AudioToolbox
• By default licensed under LGPL v3.0, libraries with -gpl postfix licensed under GPL v3.0

Packages

min: Includes only ffmpeg
min-gpl: Includes ffmpeg with all GPL licensed external libraries enabled (x264, xvidcore)
https: Includes ffmpeg with gnutls enabled
https-gpl: Includes ffmpeg with gnutls and all GPL licensed external libraries enabled (x264, xvidcore)
full: Includes ffmpeg with all external libraries without GPL license enabled
full-gpl: Includes ffmpeg with all external libraries, with or without GPL license, enabled

External Libraries

• fontconfig v2.12.93
• freetype v2.9
• fribidi v1.0.1
• gmp v6.1.2
• gnutls v3.5.18
• kvazaar v1.2.0
• lame v3.100
• libass v0.14.0
• libiconv v1.15
• libilbc v2.0.2
• libtheora v1.1.1
• libvorbis v1.3.5
• libvpx v1.7.0
• libwebp v0.6.1
• libxml2 v2.9.7
• opencore-amr v0.1.5
• opus v1.2.1
• shine v3.1.1
• snappy v1.1.7
• speex v1.2.0
• wavpack v5.1.0
• (*) x264 v20180606-2245-stable
• (*) xvidcore v1.3.5

(*): Libraries with GPL license