Added a fix that allows newly-constructed objects

to returned by expressions, by removing the
__cxa_atexit call that would normally cause these
objects to be destroyed.  This also prevents many
errors of the form

Couldn't rewrite one of the arguments of a function call
error: Couldn't materialize struct: Structure hasn't been laid out yet

<rdar://problem/11309402>

llvm-svn: 160596