ffserver_config: improve error handling

Replace atoi with more advanced parsing routine.
Set maximum port value to 65535 (not 65536).
Other checks.

Signed-off-by: Lukasz Marek <lukasz.m.luki2@gmail.com>
ffserver_config: improve AVOption handing

AVOption are checked right after found in config file.
It allows to report exact line in config file.

Options provided more than once are threated as errors.

It also fixes flag options handing.
Flags may occur more than once in config file.

Signed-off-by: Lukasz Marek <lukasz.m.luki2@gmail.com>
lavf/movenc: Write G.726 bitrate to make the files decodable.

Fixes ticket #4069.
Silence warnings for fic files with zero-sized cursors.

Fixes ticket #4072.