Do not use reserved identifiers of the C standard (See 7.1.3 Reserved identifiers)

m-string.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 __M_STRING_H
-#define __M_STRING_H
+#ifndef MSTARLIB_STRING_H
+#define MSTARLIB_STRING_H
 
 #include <ctype.h>
 #include <stdio.h>