Patch adding move constructors and move assignments

[Antony Polukhin]

Use of move constructor and move assignment reduce memory allocation/deallocations count and do not call functor copy operator for big functors. Example:

struct big_aggregating_structure {
    int disable_small_objects_optimizations[32];
    
    void operator()() {}
};

...

function<void()> f1 = big_aggregating_structure();
function<void()> f2 = f1; // will call new, copy()
function<void()> f3 = std::move(f1); // Just swaps pointers, leaves f1 empty
f3 = f2; // Will call new, copy(), destory(), delete
f3 = std::move(f2); // Just swaps pointers, leaves f2 empty (calls destory(), delete for f3)

{
    function<void()> f_new1 = big_aggregating_structure();
    function<void()> f_new2 = std::move(f_new1);
    // Without move constructor, there will be additional new, copy(), destroy(), delete calls
}

This patch could be very usefull for boost::asio, boost::thread and anyone, who uses boost::function in STL containers on C++11 compilers. Patch was tested on MSVC2010, GCC-4.6

[Antony Polukhin]

(In [80552]) Add move assignment and move constructors to Boost.Function (refs #7330)

[Antony Polukhin]

(In [80738]) Merge from trunk: added move assignment and move constructors to Boost.Function (fixes #7330)