(bug 42337) Simplify "my talk" link logic in personal tools

(bug 42337) Simplify "my talk" link logic in personal tools

Another attempt at fixing the complexity and the broken RTL display
that change I822a7390 introduced.

This commit is the same as Change I36ec3bec, except that it completely
removes the parentheses that were added to the "talk" link and
the associated mytalk-parenthetical message.

The following is copied from the commit message of Change I36ec3bec:

Change I822a7390 introduced a somewhat complex way to display
the "talk" link in parentheses after the username. It would only
work in Vector, and it broke the display in RTL wikis, because
it hacked into the personal links array.

This change attempts to make it more robust, by keeping the
array intact. This fixes the display in RTL wikis.

This commit also eliminates the global $wgVectorCombineUserTalk,
which is not needed any more.

Change-Id: Ib6076396d7f5bbdd4ba771b21020bdbb8e0c5b2d