CMake: bump minimum requirement to 3.5

CMake 3.5.0 was released in March 2016.

CHANGELOG.rst

@@ -27,7 +27,7 @@ Improved terminal support
 
 For distributors
 ----------------
-- *This placeholder silences a sphinx doc warning, so the last section is not empty.*
+- The minimum version of CMake required to build fish was raised to 3.5.0.
 
 --------------
  

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.2)
+cmake_minimum_required(VERSION 3.5)
 
 if(POLICY CMP0066)
   cmake_policy(SET CMP0066 OLD)

README.rst

@@ -143,7 +143,7 @@ Dependencies
 Compiling fish requires:
 
 -  a C++11 compiler (g++ 4.8 or later, or clang 3.3 or later)
--  CMake (version 3.2 or later)
+-  CMake (version 3.5 or later)
 -  a curses implementation such as ncurses (headers and libraries)
 -  PCRE2 (headers and libraries) - a copy is included with fish
 -  gettext (headers and libraries) - optional, for translation support

cmake/ConfigureChecks.cmake

@@ -56,10 +56,6 @@ endif()
 
 # Get threads.
 set(THREADS_PREFER_PTHREAD_FLAG ON)
-# FindThreads < 3.4.0 doesn't work for C++-only projects
-if(CMAKE_VERSION VERSION_LESS 3.4.0)
-    enable_language(C)
-endif()
 find_package(Threads REQUIRED)
 
 # Detect WSL. Does not match against native Windows/WIN32.