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-static_assert.cpp

@@ -0,0 +1,5 @@
+int main(void)
+{
+	static_assert(0 < 1, "your ordering of integers is screwed");
+	return 0;
+}