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-cstdint.cpp

@@ -0,0 +1,11 @@
+#include <cstdint>
+
+int main()
+{
+	bool test =
+		(sizeof(int8_t) == 1) &&
+		(sizeof(int16_t) == 2) &&
+		(sizeof(int32_t) == 4) &&
+		(sizeof(int64_t) == 8);
+	return test ? 0 : 1;
+}