mkvmuxer: Fix hard-coded data size in EbmlElementSize

EbmlElementSize for char* assumes that the varint encoding of
payload size is always 1-byte. Fix that by using the correct
number of bytes.

mkvinfo of the new gold file: http://pastebin.com/ncR7DqEf

Change-Id: I2d10708de77b2b8089900a8719ee3797dfb6994c
4 files changed