Filip Roséen authored Nov 16, 2016 and François Cartegnie committed Nov 16, 2016

MP4_ReadBox_String is invoked for boxes that contains raw
byte-content, though there is nothing saying that this raw-byte
sequence does not contain a null-byte ('\0').

If the sequence contains a null-byte, then there is no way (in the
previous implementation) for things working with the box-content to
access data that follows it (given that one cannot know if the
null-byte is the end-of-data terminator, or simply part of the
payload).

These changes make sure that the entire contents can be accessed by
including the length of the contents in MP4_Box_data_string_t.

Signed-off-by: Francois Cartegnie <fcvlcdev@free.fr>