Simplify cmake threads detection on Windows

Requires cmake 3.1.

CMakeLists.txt

@@ -4,7 +4,7 @@
 # To configure the build options either use the CMake gui, or run the command
 # line utility including the "-i" option.
 
-cmake_minimum_required(VERSION 3.0)
+cmake_minimum_required(VERSION 3.1)
 cmake_policy(SET CMP0042 NEW)
 
 project(mosquitto)
@@ -67,18 +67,9 @@ option(WITH_THREADING "Include client library threading support?" ON)
 if (WITH_THREADING)
 	add_definitions("-DWITH_THREADING")
 	if (WIN32)
-		if (CMAKE_VERSION VERSION_LESS "3.1")
-			if (CMAKE_CL_64)
-				set (PTHREAD_LIBRARIES C:\\pthreads\\Pre-built.2\\lib\\x64\\pthreadVC2.lib)
-			else (CMAKE_CL_64)
-				set (PTHREAD_LIBRARIES C:\\pthreads\\Pre-built.2\\lib\\x86\\pthreadVC2.lib)
-			endif (CMAKE_CL_64)
-			set (PTHREAD_INCLUDE_DIR C:\\pthreads\\Pre-built.2\\include)
-		else()
 		find_package(Threads REQUIRED)
 		set (PTHREAD_LIBRARIES Threads::Threads)
 		set (PTHREAD_INCLUDE_DIR "")
-		endif()
 	elseif (ANDROID)
 		set (PTHREAD_LIBRARIES "")
 		set (PTHREAD_INCLUDE_DIR "")

ChangeLog.txt

@@ -6,6 +6,10 @@ Broker:
   MOSQ_EVT_MESSAGE.
 - Fix bridge `restart_timeout` not being honoured.
 
+Client library:
+- Fix threads library detection on Windows under cmake. Bumps the minimum
+  cmake version to 3.1, which is still ancient.
+
 
 2.0.14 - 2021-11-17
 ===================