initial commit, 4.5 stable

thirdparty/doctest/patches/0001-ciso646-version.patch

@@ -0,0 +1,24 @@
+diff --git a/thirdparty/doctest/doctest.h b/thirdparty/doctest/doctest.h
+index 52b4a4aa30..4a1e4a09d7 100644
+--- a/thirdparty/doctest/doctest.h
++++ b/thirdparty/doctest/doctest.h
+@@ -490,13 +490,17 @@ DOCTEST_GCC_SUPPRESS_WARNING_POP
+ #endif
+ #endif // DOCTEST_CONFIG_USE_IOSFWD
+ 
+-// for clang - always include ciso646 (which drags some std stuff) because
+-// we want to check if we are using libc++ with the _LIBCPP_VERSION macro in
++// for clang - always include <version> or <ciso646> (which drags some std stuff)
++// because we want to check if we are using libc++ with the _LIBCPP_VERSION macro in
+ // which case we don't want to forward declare stuff from std - for reference:
+ // https://github.com/doctest/doctest/issues/126
+ // https://github.com/doctest/doctest/issues/356
+ #if DOCTEST_CLANG
++#if DOCTEST_CPLUSPLUS >= 201703L && __has_include(<version>)
++#include <version>
++#else
+ #include <ciso646>
++#endif
+ #endif // clang
+ 
+ #ifdef _LIBCPP_VERSION