After this change, the relation between copy/move constructor calls in QtGui is
something like 40/16.
A moved-from QPen can only be copied, assigned-to or else destroyed. This required
adding a nullptr check to the copy ctor and the dtor and rewriting copy assignment
(which used non-nullptr-safe qAtomicAssign) in terms of copy construction and
swapping.
Extensive tests included. They are implemented such that they work in C++98 as well
as C++11 mode, but they naturally test move semantics only in a C++11 build.
Change-Id: If68f37c10b8eeefb2478cbae386cd2e38b4f6e19
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
db8167c224