Test test3_mvov failed when running in clang and clang-cl on Windows

Hi,
I found that [Test test3_mvov](https://github.com/boostorg/ublas/blob/master/IDEs/qtcreator/test/test3_mvov.pro) failed for map/set iterators incompatible in clang and clang-cl on Windows.
Below are the commands that I used.
```
clang test3.cpp -o test3.obj -std=c++17 -D_CRT_USE_BUILTIN_OFFSETOF -c -DBOOST_ALL_NO_LIB=1 -DBOOST_UBLAS_NO_EXCEPTIONS -DUSE_DOUBLE -DUSE_FLOAT -DUSE_MAPPED_VECTOR_OF_MAPPED_VECTOR -DUSE_STD_COMPLEX -DUSE_STD_MAP -I"..\..\..\.."
clang test31.cpp -o test31.obj -std=c++17 -D_CRT_USE_BUILTIN_OFFSETOF -c -DBOOST_ALL_NO_LIB=1 -DBOOST_UBLAS_NO_EXCEPTIONS -DUSE_DOUBLE -DUSE_FLOAT -DUSE_MAPPED_VECTOR_OF_MAPPED_VECTOR -DUSE_STD_COMPLEX -DUSE_STD_MAP -I"..\..\..\.."
clang test32.cpp -o test32.obj -std=c++17 -D_CRT_USE_BUILTIN_OFFSETOF -c -DBOOST_ALL_NO_LIB=1 -DBOOST_UBLAS_NO_EXCEPTIONS -DUSE_DOUBLE -DUSE_FLOAT -DUSE_MAPPED_VECTOR_OF_MAPPED_VECTOR -DUSE_STD_COMPLEX -DUSE_STD_MAP -I"..\..\..\.."
clang test33.cpp -o test33.obj -std=c++17 -D_CRT_USE_BUILTIN_OFFSETOF -c -DBOOST_ALL_NO_LIB=1 -DBOOST_UBLAS_NO_EXCEPTIONS -DUSE_DOUBLE -DUSE_FLOAT -DUSE_MAPPED_VECTOR_OF_MAPPED_VECTOR -DUSE_STD_COMPLEX -DUSE_STD_MAP -I"..\..\..\.."
clang -o test3 test3.obj test31.obj test32.obj test33.obj
./test3
```
I got lots of warnings when compiling `test32.cpp` and `test33.cpp`, which look like this.
```
In file included from test33.cpp:13:
In file included from ./test3.hpp:18:
In file included from ..\..\..\..\boost/numeric/ublas/vector.hpp:21:
In file included from ..\..\..\..\boost/numeric/ublas/storage.hpp:26:
In file included from ..\..\..\..\boost/numeric/ublas/traits.hpp:21:
..\..\..\..\boost/numeric/ublas/detail/iterator.hpp:149:21: warning: 'iterator, long long, std::complex *, std::complex &>' is deprecated: warning STL4015: The std::iterator
class template (used as a base class to provide typedefs) is deprecated in C++17. (The header is NOT deprecated.) The C++ Standard has never required user-defined iterators to derive from std::iterator. To fix this warning, stop deriving from
std::iterator and start providing publicly accessible typedefs named iterator_category, value_type, difference_type, pointer, and reference. Note that value_type is required to be non-const, even for constant iterators. You can define
_SILENCE_CXX17_ITERATOR_BASE_CLASS_DEPRECATION_WARNING or _SILENCE_ALL_CXX17_DEPRECATION_WARNINGS to acknowledge that you have received this warning. [-Wdeprecated-declarations]
public std::iterator {
^
```
And I also got the following output and a window which showed me the debug assertion failing message when running the exeutable file `test3`.
```
test_vector
test_matrix_vector
float mapped_vector_of_mapped_vector
row (m, 0) = [3](1,2,3)
```
As the warnings tell us, should the source code be modified to fix this issue?
Thanks!

Start with IDEs/qtcreator/test/test3_mvov.pro and reproduce the listed clang commands for test3.cpp, test31.cpp, test32.cpp, and test33.cpp on Windows. Read boost/numeric/ublas/detail/iterator.hpp alongside the failing test output, then determine whether the std::iterator warnings relate to the assertion. Done means test3 runs without the reported assertion, with the warning impact explained or addressed.

Written by the indexing model from the issue text.