Add C++11 compiler support detection feature

This is currently copied from http://quickgit.kde.org/index.php?p=scratch%2Fdakon%2Fcmake-cxx11.git
but there is a chance that in future it will be merged into CMake proper.

cmake/Modules/CheckCXX11Features/cxx11-test-auto.cpp

@@ -0,0 +1,12 @@
+
+int main()
+{
+	auto i = 5;
+	auto f = 3.14159f;
+	auto d = 3.14159;
+	bool ret = (
+		(sizeof(f) < sizeof(d)) &&
+		(sizeof(i) == sizeof(int))
+	);
+	return ret ? 0 : 1;
+}