Add a configuration option for threadapi=pthread/win32, set the defau…

…lt properly on Cygwin

Merge pull request boostorg#317 from eldiener/develop

Changes for Embarcadero C++ clang-based compilers, targeting Boost 1.74

Merge pull request boostorg#317 from eldiener/develop

Changes for Embarcadero C++ clang-based compilers, targeting Boost 1.74

Merge pull request boostorg#317 from eldiener/develop

Changes for Embarcadero C++ clang-based compilers, targeting Boost 1.74

Merge pull request boostorg#317 from eldiener/develop

Changes for Embarcadero C++ clang-based compilers, targeting Boost 1.74

Add msvc-14.2/release to Appveyor

Add msvc-14.2/release to Appveyor

Update appveyor.yml

Merge pull request boostorg#299 from Kojoley/winapi-deprecated-namespace

Switch out from using deprecated Winapi namespace

Merge branch 'develop'