lavf/qtpalette: Treat 1-bit video as palettized

This commit for qtpalette.c and qtpalette.h adds 1-bit video to the
"palettized video" category, since if the video sample description
contains a palette, the two colors in the palette can be any color, not
necessarily black & white.

Unfortunately, I've noticed that the qtrle (QuickTime Animation) decoder
blindly assumes that 1-bit video is black & white. I don't have enough
knowledge about the decoder to fix this, though.

Below is a link to a sample 1-bit QuickTime Animation clip of a rotating
earth that uses blueish colors, and they will be correctly rendered in
QuickTime, but not in FFmpeg (which will use black & white).

https://drive.google.com/open?id=0B3_pEBoLs0faUlItWm9KaGJSTEE



Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>