Fix for clang memcpyizer bugs 23911 and 23924 (patch by Denis Zobnin)

The fix is to remove duplicate copy-initialization of the only memcpy-able struct member and to correct the address of aggregately initialized members in destructors' calls during stack unwinding (in order to obtain address of struct member by using GEP instead of 'bitcast').
Differential Revision: http://reviews.llvm.org/D10990

llvm-svn: 242127