This replaces the `std::get` call with an unqualified equivalent to allow
it to be treated as a dependent call.

ranges.h needs std::get overloads from `<tuple>` but does not directly
include it. This causes compilation failures in MSVC with /permissive-.
On other platforms `<tuple>` is included as a dependency from other headers
(specifically from `<memory>`), but there is no such implicit dependency in
MSVC's STL.

Fixes #2401

* suppress unused variable warnings

An arguably better method for suppressing unused variable warnings.   The `(void)var` method does not work on many intel compiilers.
This is from Herb Sutter's blog post https://herbsutter.com/2009/10/18/mailbag-shutting-up-compiler-warnings/

* Format to eliminate long lines

* Run clang-format

For what I see this seems unused?

Adjust definition for FMT_HAS_INCLUDE

Remove check for `!FMT_MSC_VER`

The udl_{arg,formatter} structs are only defined when
FMT_USE_USER_DEFINED_LITERALS is set, so don't try to define things that
return that struct when it's not defined.

The intel compiler defines `__GNUC__`, but does not support the gcc `_Pragma`.  This PR filters out the intel compiler to avoid warnings about an unrecognized function.

 * do this  in _some_ tests to improve test coverage and catch possible problems due to that
 * fix invalid export of `static constexpr` constant
 * fix msvc warnings about unreachable code in high warning levels