This patch backports the recent firstprivate subarray changes I've made
to trunk. Gomp4 has preliminary support for c++ reference types, so I
had to make some adjustments to the original patch to get this.C and
non-scalar-data.C working. Those changes were relatively minor, so I'll
bring them to trunk after I address the remarks Thomas made on my
original patch.

Thomas, I decided to xfail a bunch of kernels tests in gomp4 instead of
removing them so that we can have a better record on what changed. One
of use should investigate why the alias analysis doesn't like the
firstprivate pointer changes.

Cesar