Convert use of _nc() to _nx()
|Reported by:||nacin||Owned by:||westi|
_c() was deprecated for _x(). Core still uses _nc() in one spot, however. Patch moves that over to _nx().
Patch also formally deprecates _nc() and moves it to deprecated.php, next to its sibling _c().
I imagine other deprecated moves can be handled in #11388 for 3.0.