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-rvalue-references.cpp

@@ -0,0 +1,57 @@
+#include <cassert>
+
+class rvmove {
+public:
+   void *ptr;
+   char *array;
+
+   rvmove()
+    : ptr(0),
+    array(new char[10])
+   {
+     ptr = this;
+   }
+
+   rvmove(rvmove &&other)
+    : ptr(other.ptr),
+    array(other.array)
+   {
+    other.array = 0;
+    other.ptr = 0;
+   }
+
+   ~rvmove()
+   {
+    assert(((ptr != 0) && (array != 0)) || ((ptr == 0) && (array == 0)));
+    delete[] array;
+   }
+
+   rvmove &operator=(rvmove &&other)
+   {
+     delete[] array;
+     ptr = other.ptr;
+     array = other.array;
+     other.array = 0;
+     other.ptr = 0;
+     return *this;
+   }
+
+   static rvmove create()
+   {
+     return rvmove();
+   }
+private:
+  rvmove(const rvmove &);
+  rvmove &operator=(const rvmove &);
+};
+
+int main()
+{
+  rvmove mine;
+  if (mine.ptr != &mine)
+    return 1;
+  mine = rvmove::create();
+  if (mine.ptr == &mine)
+    return 1;
+  return 0;
+}