Revert some silly renamings that leaked in from a pull.
Merge remote-tracking branch 'newdev/master'
doc: update build system documentation
Split normal build system documentation and the fate one.
Document THREADS make variable and provide an introduction to fate.Document DESTDIR make variable and add some generic targets.
Revert "replace FFmpeg with Libav in doc/"
This reverts commit f8a45fa1b1764b34d4263eacd93411e8ba0484a4.
replace FFmpeg with Libav in doc/
unless it stands for ffmpeg the program or is historic
document passing the fate samples location via make variable
custom build system documentation
Originally committed as revision 25375 to svn://svn.ffmpeg.org/ffmpeg/trunk