Don't enable C language in CMake

spdlog doesn't seem to actually require the C language.
Not enabling it results in a significant initial configure time speedup.

CMakeLists.txt

 # Copyright(c) 2019 spdlog authors Distributed under the MIT License (http://opensource.org/licenses/MIT)
 
-cmake_minimum_required(VERSION 3.13)
-enable_language(C)
+cmake_minimum_required(VERSION 3.10)
 
 # ---------------------------------------------------------------------------------------
 # Start spdlog project

bench/CMakeLists.txt

 # Copyright(c) 2019 spdlog authors Distributed under the MIT License (http://opensource.org/licenses/MIT)
 
-cmake_minimum_required(VERSION 3.13)
+cmake_minimum_required(VERSION 3.10)
 project(spdlog_bench CXX)
 
 if(NOT TARGET spdlog)

example/CMakeLists.txt

 # Copyright(c) 2019 spdlog authors Distributed under the MIT License (http://opensource.org/licenses/MIT)
 
-cmake_minimum_required(VERSION 3.13)
+cmake_minimum_required(VERSION 3.10)
 project(spdlog_examples CXX)
 
 if(NOT TARGET spdlog)

tests/CMakeLists.txt

-cmake_minimum_required(VERSION 3.13)
+cmake_minimum_required(VERSION 3.10)
 project(spdlog_utests CXX)
 
 if (NOT TARGET spdlog)