Wrong behavior of map_array copy constructor.

map_array copy constructor is not functions as expected, leading to crash.

Code to reproduce:

```C++
boost::numeric::ublas::map_array getMapArray()
{
boost::numeric::ublas::map_array ma;
ma.insert(std::make_pair(1, 1.0f));

return ma;
}

int main()
{
boost::numeric::ublas::map_array ma = getMapArray();
return 0;
}

```
Fix:
in line 248 of storage_sparse.hpp,
```C++
//std::uninitialized_copy (data_, data_ + capacity_, c.data_); // original implementation
std::uninitialized_copy (c.data_, c.data_ + c.size_, data_);
```