Merge remote-tracking branch 'qatar/master'

* qatar/master:
  lavu: avoid clashing definition of E
  doc: developer: Add a note about reserved system name space

Conflicts:
	libavutil/internal.h

Merged-by: Michael Niedermayer <michaelni@gmx.at>

diff --cc doc/developer.texi
Simple merge

diff --cc libavutil/internal.h
Simple merge