[theora] python bindings to libtheora

[ogg.k.ogg.k at googlemail.com]

> Many thanks for the patch! It's now in. How can I install theora, so
> that pkg-config knows about it?
[...]
> $ cat /home/ondrej/ext/libtheora-1.0/theoraenc.pc
[...]
> $ pkg-config --exists theoraenc theoradec

$ PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/home/ondrej/ext/libtheora-1.0
pkg-config --exists theoraenc theoradec

or

$ PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/home/ondrej/usr/lib/pkg-config
pkg-config --exists theoraenc theoradec