Previously a short circuiting && chain would drop the
first element after all the other elements, and otherwise
follow evaluation order, so code like:

f(1).g() && f(2).g() && f(3).g() && f(4).g()

would drop the temporaries in the order 2,3,4,1. This made
&& and || non-associative regarding drop order, so
adding ()'s to the expression would change drop order:

f(1).g() && (f(2).g() && f(3).g()) && f(4).g()

for example would drop in the order 3,2,4,1.

As, except for the bool result, there is no data returned
by the sub-expressions of the short circuiting binops,
we can safely discard of any temporaries created by the
sub-expr. Previously, code was already putting the rhs's
into terminating scopes, but missed it for the lhs's.

This commit addresses this "twist". In the expression,
we now also put the lhs into a terminating scope.
The drop order for the above expressions is 1,2,3,4
now.

This avoids creation of a terminating scope in
chains that contain both && and ||, because
also there we know that a terminating scope is
not neccessary: all the chain members are already
in such terminating scopes.

Also add a mixed && / || test.