Co-authored-by: Stephan T. Lavavej <stl@nuwen.net>

Co-authored-by: Stephan T. Lavavej <stl@nuwen.net>

Co-authored-by: Stephan T. Lavavej <stl@microsoft.com>

…1452)

Co-authored-by: Stephan T. Lavavej <stl@microsoft.com>

Co-authored-by: Stephan T. Lavavej <stl@microsoft.com>

Co-authored-by: Casey Carter <cacarter@microsoft.com>
Co-authored-by: Curtis Jacques Bezault <curtbezault@gmail.com>
Co-authored-by: Stephan T. Lavavej <stl@microsoft.com>

…constructor (microsoft#1510)

Co-authored-by: Stephan T. Lavavej <stl@microsoft.com>

…r<true> (microsoft#1458)

Co-authored-by: Stephan T. Lavavej <stl@microsoft.com>
Co-authored-by: Casey Carter <cartec69@gmail.com>

Co-authored-by: Casey Carter <cacarter@microsoft.com>

Co-authored-by: Stephan T. Lavavej <stl@microsoft.com>

…1494)

Co-authored-by: Stephan T. Lavavej <stl@microsoft.com>
Co-authored-by: Casey Carter <cartec69@gmail.com>

…#1509)

Co-authored-by: Casey Carter <cacarter@microsoft.com>

Co-authored-by: Stephan T. Lavavej <stl@microsoft.com>

* Fix microsoft#1471 by properly waiting for the Windows Driver Kit installation to finish.
* Update `azure-pipelines.yml` to use the new pool `StlBuild-2020-12-08`.
* Update `README.md` to mention Preview 2. (Its CMake and Ninja versions haven't changed,
  and we don't directly mention the Clang version.)
* Update `yvals_core.h` to require Clang 11. (Note that MSVC's `_MSC_VER` is remaining `1928` for the 16.9 release.)
* Remove the workaround for LLVM-37556. (We were treating it as an uncommented perma-workaround, but I remembered.)
* Remove many workarounds in `P1502R1_standard_library_header_units`.
* Remove the VSO-1225825 workaround in `<iterator>` and `<ranges>`.
* Unrelated cleanup in `<valarray>`: `__cpp_aligned_new` implies `if constexpr`.
* Update the vcpkg submodule for Boost 1.74.0. This is just their latest commit.
* In `CMakeLists.txt`, require Boost 1.74.0. (This, combined with the toolset update,
  implies that contributors will need to `git submodule update`, clean out the `vcpkg`
  submodule with `git clean -x -d -f`, and then bootstrap vcpkg and build boost-math.)
* Simplify conditional operators in `seed_seq::generate`.
  + Thanks to @AlexGuteniev for suggesting extracting `_Off` and noticing
    that `_Myvec[(_Kx - 1) % _Sx]` was unnecessarily complicated. Given `_Kx` in `[1, _Sx]`,
    then `_Kx - 1` is in `[0, _Sx - 1]`, so `% _Sx` does nothing.
* Take advantage of clang-format 11. This sets `AlignOperands: AlignAfterOperator` and `IndentCaseBlocks: true`.