In C++98/03, when binding a reference to an rvalue of

reference-compatible type, the implementation is permitted to make a
copy of the rvalue (or many such copies, even). However, even though
we don't make that copy, we are required to check for the presence of
a suitable copy constructor. With this change, we do.

Note that in C++0x we are not allowed to make these copies, so we test
both dialects separately.

Also note the FIXME in one of the C++03 tests, where we are not
instantiating default function arguments for the copy constructor we
pick (but do not call). The fix is obvious; eliminating the infinite
recursion it causes is not. Will address that next.

llvm-svn: 101704