sprintf replacement: introduce au_snprintf to support snprintf for v2013

and earier ( closes https://github.com/assimp/assimp/issues/743 )

code/FixNormalsStep.cpp

@@ -45,6 +45,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // internal headers
 #include "FixNormalsStep.h"
+#include "StringUtils.h"
 #include "../include/assimp/DefaultLogger.hpp"
 #include "../include/assimp/postprocess.h"
 #include "../include/assimp/scene.h"
@@ -158,7 +159,7 @@ bool FixInfacingNormalsProcess::ProcessMesh( aiMesh* pcMesh, unsigned int index)
         if (!DefaultLogger::isNullLogger())
         {
             char buffer[128]; // should be sufficiently large
-            ::sprintf(buffer,"Mesh %u: Normals are facing inwards (or the mesh is planar)",index);
+            ai_snprintf(buffer,128,"Mesh %u: Normals are facing inwards (or the mesh is planar)",index);
             DefaultLogger::get()->info(buffer);
         }