Avoid using '__' within words.

It seems to be a reserved naming of C++.

m-i-shared.h

@@ -22,8 +22,8 @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
-#ifndef MSTARLIB_I_SHARED_PTR__H
-#define MSTARLIB_I_SHARED_PTR__H
+#ifndef MSTARLIB_I_SHARED_PTR_H
+#define MSTARLIB_I_SHARED_PTR_H
 
 #include "m-core.h"
 #include "m-atomic.h"