Make max_contextid field match same type as cid in communicator.

Refs trac:1904

This commit was SVN r21141.

The following Trac tickets were found above:
  Ticket 1904 --> https://svn.open-mpi.org/trac/ompi/ticket/1904

ompi/communicator/comm_cid.c

@@ -156,7 +156,7 @@ int ompi_comm_nextcid ( ompi_communicator_t* newcomm,
         int done=0;
         int response, glresponse=0;
         int start;
-        int i;
+        unsigned int i;
         
         do {
             /* Only one communicator function allowed in same time on the

ompi/mca/pml/pml.h

@@ -507,7 +507,7 @@ struct mca_pml_base_module_1_0_0_t {
     mca_pml_base_module_ft_event_fn_t     pml_ft_event;
 
     /* maximum constant sizes */
-    int                                   pml_max_contextid;
+    uint32_t                              pml_max_contextid;
     int                                   pml_max_tag;
 };
 typedef struct mca_pml_base_module_1_0_0_t mca_pml_base_module_1_0_0_t;