Skip locales triggering the mbstowcs() bug. I collected the locale list thanks
my previous commit:

 * hu_HU (ISO8859-2): character U+30000020
 * de_AT (ISO8859-1): character U+30000076
 * cs_CZ (ISO8859-2): character U+30000020
 * sk_SK (ISO8859-2): character U+30000020
 * pl_PL (ISO8859-2): character U+30000020
 * fr_CA (ISO8859-1): character U+30000020