NUM_WORDS and ORDINAL_WORDS are currently not used, but the hard-coded
list should be removed from orth.pyx and replaced to use
language-specific functions. This will later allow other languages to
use their own functions to set those flags. (In English, this is easier
because it only needs to be checked against a set – in German for
example, this requires a more complex function, as most number words
are one word.)
