Following up on my long standing threat to remove internal_link hook. Templates...

Following up on my long standing threat to remove internal_link hook.  Templates make it unnecessary, it is inefficient, and the only plugin using it requires a source patch to the same code anyway.

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@8397 7612ce4b-ef26-0410-bec9-ea0150e637f0