If an AVFormatContext could be allocated, but white-/blacklists couldn't
be copied, the AVFormatContext would leak as it was only accessible
through a local variable that goes out of scope when one goes to fail.

Furthermore, in case writing a header of a submuxer failed, the options
used for said call could leak.

Both of these memleaks have been fixed.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>