ucurr_forLocale() and ucurr_forLocaleAndDate()
should share a fair bit of code.
They set a U_MISSING_RESOURCE_ERROR if the country code
is not listed in the resource bundle.
Please make them just return 0 in that case.
If the locale ID does not have a region code,
then these functions should call the "add likely subtags"
function to try to get one.