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-sizeof_member_fail.cpp

@@ -0,0 +1,9 @@
+struct foo {
+	int baz;
+	double bar;
+};
+
+int main(void)
+{
+	return (sizeof(foo::bar) == 4) ? 0 : 1;
+}