Allows the user to reserve space for the ODML master index. A sufficient
sized master index in the AVI header avoids storing follow-up master
indexes within the 'movi' data later. If the option is omitted or zero
the index size is estimated from output duration and bitrate.
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Tobias Rapp <t.rapp@noa-archive.com>