This adds a function to retrieve the number of entries in a
dictionary and updates the places directly accessing what should
be an opaque struct to use this new function instead.
Signed-off-by: Mans Rullgard <mans@mansr.com>

Signed-off-by: Martin Storsjö <martin@martin.st>

Introduce a basic layout, the subpages are currently left empty.

Split libavutil in multiple groups as example of the structure

achive -> achieve

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

Correct copyright notices.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Rename it to AVDictionary, since it will be used as such.  Tags
documentation and metadata conversion API is lavf-specific, so remains
there.