Language fallback from Pontic (pnt) to Greek (el)

Language fallback from Pontic (pnt) to Greek (el)

The (relative) majority of speakers is estimated to live in Greece
and know Greek; for the others, intelligibility seems assured.
The language fallback was probably forgotten for a mere oversight.

https://translatewiki.net/wiki/Thread:Portal_talk:Pnt/Use_Greek_when_no_translation

In addition to the discussion between translators, every pnt.wiki
user has been alerted individually.

From el, pnt will inherit hundreds of translations for magic words,
namespaces and special page names. $linkTrail, $separatorTransformTable
and $fallback8bitEncoding are currently defined in el but not pnt.
The "ISO 8601" date format will also change definition, but the default
date format is "pnt" which is defined only for pnt.

Change-Id: I0377fff9300a8314cb9172f3be710be5dbce6825