Merge pull request #777 from band-a-prend/cmake_mpi_c

CMake: fix -Wint-conversion warning (error if clang is used as MPIC_C)

Author: zbeekman

CMakeLists.txt

@@ -426,7 +426,7 @@ int main(int argc, char** argv) {
   char processor_name[MPI_MAX_PROCESSOR_NAME];
   int name_len;
   MPI_Get_processor_name(processor_name, &name_len);
-  printf('Hello world from processor %s, rank %d out of %d processors',
+  printf(\"Hello world from processor %s, rank %d out of %d processors\",
          processor_name, world_rank, world_size);
   MPI_Finalize();
 }"