CMake: check if the compiler supports using precompiled headers

Build the cotire test project and check if it succeeds. Also check if the
'had text segment at different address' warning does not appear in the build
output. If it does not succeed, disable usage of precompiled headers.

If the PCH option was changed, clean the project and rebuild it again. Do not
clean everytime the project is configured because (re)building the cotire test
project takes some time.

build/cmake/modules/cotire_test/CMakeLists.txt

@@ -0,0 +1,21 @@
+# cotire example project
+
+cmake_minimum_required(VERSION 2.8.12)
+
+if (POLICY CMP0058)
+	# Ninja requires custom command byproducts to be explicit
+	cmake_policy(SET CMP0058 NEW)
+endif()
+
+project (CotireExample)
+
+set (CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}/..")
+
+if (NOT CMAKE_VERSION VERSION_LESS "3.1.0")
+	set (CMAKE_CXX_STANDARD "98")
+	set (CMAKE_CXX_EXTENSIONS OFF)
+endif()
+
+include(cotire)
+
+add_subdirectory(src)