<rdar://problem/10020849>

Fixed an issue where the DWARF might mention that a class has a constructor
(default, copy or move), destructor, or an assignment operator (copy or move)
and it might not have an actual implementation in your code. Then you try and
use this struct or class in an expression and the JIT would ask for the 
address of these methods that were in the declaration, yet there are none.
We now "do the right thing" for trivial ctors, dtors and assignment operators
by telling the methods that they are are defaulted and trivial, and clang will
then just do all of the work with builtins!

llvm-svn: 143528