Call PerformCopyInitialization to properly initialize the exception temporary

in a throw expression.  Use EmitAnyExprToMem to emit the throw expression,
which magically elides the final copy-constructor call (which raises a new
strict-compliance bug, but baby steps).  Give __cxa_throw a destructor pointer
if the exception type has a non-trivial destructor.

llvm-svn: 102039