Cleanup some incorrect return annotations

Most of these are simply changing annotations to reflect
reality. If a function can return false to indicate failure
the @return should indicate it.

Some are fixing preg_match calls, preg match returns 1, 0 or false,
but the functions all claim to return booleans.

This is far from all the incorrect return types in mediawiki, there
are around 250 detected by phan, but have to start somewhere.

Change-Id: I1bbdfee6190747bde460f8a7084212ccafe169ef