Cast various things that are supposed to be ints

Cast various things that are supposed to be ints

Mysqli is returning SELECTed ints as strings rather than as ints, I'm
guessing to avoid problems with 64-bit int types on 32-bit systems. PHP
mostly doesn't care, but it causes API JSON output to have strings
instead of ints all over the place.

This also fixes ForeignAPIFile::getUser( 'id' ) returning the user
*name*.

Bug: T98276
Change-Id: Ie6591d72b3ac40172f8176a8ca8b6fad8e9275a5