Gah; I missed the #include in r30539.

cmr=v1.7.5:ticket=trac:4217

This commit was SVN r30540.

The following SVN revision numbers were found above:
  r30539 --> open-mpi/ompi@fb67d98867

The following Trac tickets were found above:
  Ticket 4217 --> https://svn.open-mpi.org/trac/ompi/ticket/4217

ompi/mpi/c/dims_create.c

@@ -21,6 +21,8 @@
 
 #include "ompi_config.h"
 
+#include <math.h>
+
 #include "ompi/mpi/c/bindings.h"
 #include "ompi/runtime/params.h"
 #include "ompi/communicator/communicator.h"