Make copy assignment operator synthesis not explode for classes with complex

Make copy assignment operator synthesis not explode for classes with complex
or non-record aggregate members.

It might be worth spending some time to optimize this code (and the parallel
code for copy constructors) to memcpy in larger chunks, rather than copying
one member at a time.  Not sure exactly how beneficial that would be, but
it seems like could help for large classes with, for example, a vtable pointer
forcing the generation of a copy constructor.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@90823 91177308-0d34-0410-b5e6-96231b3b80d8