tools: fix decompress function.
tools: fix decompress function.

But I will not be able to use it for compressed genicam data, since they are in
fact stored in a zip file.

lu-zero/aravis,lu-zero/aravis,lu-zero/aravis,AnilRamachandran/aravis,AnilRamachandran/aravis,AnilRamachandran/aravis,AravisProject/aravis,AnilRamachandran/aravis,AnilRamachandran/aravis,AravisProject/aravis,AravisProject/aravis,lu-zero/aravis,lu-zero/aravis,AravisProject/aravis,AravisProject/aravis