Warning C4459 when building using MSVC

[mikekaganski]

Using multi_array, MSVC (VS 2019, VS 2022) emits the following warnings (using Boost release 1.82.0, but current code in the repo includes the same global variable and argument name):

`C:\lo\build\workdir\UnpackedTarball\boost\boost/multi_array/multi_array_ref.hpp(615): warning C4459: declaration of 'extents' hides global declaration

C:\lo\build\workdir\UnpackedTarball\boost\boost/multi_array/base.hpp(69): note: see declaration of 'boost::anonymous-namespace'::extents'

This prevents warning-free builds, or requires pollution of the code with pragmas. Would it be possible to rename the constructor argument name?

[glenfe]

@mikekaganski Yes, for the 1.86 release (not the upcoming 1.85 release).