Fix Windows build with MSYS2/MinGW.

SChannelConnection depends on a C++14 feature, make_unique.

src/CMakeLists.txt

@@ -2,7 +2,7 @@ cmake_minimum_required (VERSION 3.13)
 
 ### Basic compilation settings
 set (CMAKE_POSITION_INDEPENDENT_CODE TRUE)
-set (CMAKE_CXX_STANDARD 11)
+set (CMAKE_CXX_STANDARD 14)
 
 include_directories (
 	${CMAKE_CURRENT_SOURCE_DIR}