Add tzm (ⵜⴰⵎⴰⵣⵉⵖⵜ) (Tamazight) to Names.php

The tzm.json file was committed in 2014-06-26 and has over 600 lines,
but the language can't be selected in Special:Preferences.

Change-Id: Ie362dbd46132397763382bf102b17e63c6a088cb