fr: Fix plural handling for "million" and suffixes above

Because 400000000 should be "quatre cents millions" not "quatre cent millions"
since suffixes "million", "milliard" and above are names not adjectives, and
therefore must have the plural form.

Source: http://leconjugueur.lefigaro.fr/frlesnombres.php
Merge pull request #18 from jjk-jacky/fix-fr-plural

fr: Fix plural handling for "million" and suffixes above