has_nothrow_default_constructor hooked up to clang. Filed...

has_nothrow_default_constructor hooked up to clang.  Filed http://llvm.org/bugs/show_bug.cgi?id=8101 to take care of void, arrays of incomplete types, and classes with virtual destructors which don't work yet.  If there is some reasons we don't want to handle these types in the compiler, I can handle them in the library.

llvm-svn: 113217