use c++ style include files for c-library functions

src/USER-SDPD/fix_meso_move.cpp

@@ -16,8 +16,8 @@
       Morteza Jalalvand (IASBS)  jalalvand.m AT gmail.com
 ------------------------------------------------------------------------- */
 
-#include "string.h"
-#include "math.h"
+#include <cstring>
+#include <cmath>
 #include "fix_meso_move.h"
 #include "atom.h"
 #include "group.h"

src/USER-SDPD/fix_rigid_meso.cpp

@@ -27,7 +27,7 @@
     and all codes relevant to that has been removed
 ------------------------------------------------------------------------- */
 
-#include <math.h>
+#include <cmath>
 #include "fix_rigid_meso.h"
 #include "math_extra.h"
 #include "atom.h"

src/USER-SDPD/pair_sdpd_taitwater_isothermal.cpp

@@ -18,8 +18,8 @@
     references: Espanol and Revenga, Phys Rev E 67, 026705 (2003)
 ------------------------------------------------------------------------- */
 
-#include <math.h>
-#include <stdlib.h>
+#include <cmath>
+#include <cstdlib>
 #include "pair_sdpd_taitwater_isothermal.h"
 #include "atom.h"
 #include "force.h"