COMP: Fix a couple tests so that they compile with clang compiler.

utils/tests/Cxx/TestXdmfExodusIO.cpp

@@ -6,7 +6,7 @@
 
 #include "XdmfTestDataGenerator.hpp"
 
-int main(int, char *)
+int main(int, char **)
 {
   shared_ptr<XdmfExodusWriter> exodusWriter = XdmfExodusWriter::New();
   shared_ptr<XdmfUnstructuredGrid> hexahedron =

utils/tests/Cxx/TestXdmfTopologyConverter.cpp

@@ -9,7 +9,7 @@
 #include "XdmfUnstructuredGrid.hpp"
 #include "XdmfWriter.hpp"
 
-int main(int, char *)
+int main(int, char **)
 {
   shared_ptr<XdmfTopologyConverter> converter =
     XdmfTopologyConverter::New();