Fallback chain with locale has a variant

[Kip Cole]

Based upon this discussion document it would seem there is one bug and one poor design choice in the implementation of the fallback locales.

Document Examples:

"es-AR" → "es-419" → "es" → "und"
"sr-ME" → "sr-Latn-ME" → "sr-Latn" → "und"
"ca-ES-valencia" → "ca-ES" → "ca" → "und"
"hi-Latn-IN" → "hi-Latn" → "en-IN" → "en-001" → "en" → "und"
"en-US-u-sd-usca" → "en-US" → "en" → "und"

ex_cldr implementation

• After the fallback chain of the specified locale, the default locale and its fallback chain is applied. This would seem to be different from the spec.
• The fallback chain should terminate at :und which is it is not doing
• Locales like "ca-ES-valencia" are not falling back correctly