toxav/Makefile.inc: add LIBSODIUM_* variables to flags

These are needed if libsodium paths are discovered by 'configure'. Most systems
don't need this just because libsodium is already on the header/library search
paths, but on e.g. Mac OS X this is required.

Signed-off-by: Steven Noonan <steven@uplinklabs.net>
media.h: include 'opus.h' instead of 'opus/opus.h'

The current 'opus/opus.h' works if your opus.h is in /usr/include/opus, as
/usr/include is already in the header search path. If your opus header search
path is found via pkg-config, however, you will get something like this:

  $ pkg-config --cflags opus
  -I/usr/local/Cellar/opus/1.1/include/opus

Since this is pointing directly to include/opus, the 'opus/' prefix on the
header include directive will break.

Since 'opus.h' should work in both cases (as in both cases it will be
discovered via pkg-config), just use the simpler 'opus.h'.

Signed-off-by: Steven Noonan <steven@uplinklabs.net>
Merge branch 'master' of https://github.com/tycho/ProjectTox-Core into tycho-master