[analyzer] Do not report uninitialized value warnings inside swap functions.

This silences warnings that could occur when one is swapping partially initialized structs. We suppress
not only the assignments of uninitialized members, but any values inside swap because swap could
potentially be used as a subroutine to swap class members.

This silences a warning from std::try::function::swap() on partially initialized objects.

llvm-svn: 184256