Increase the size of MPI_MAX_PORT_NAME from 256 to 1024.

Rationale:

 1. This value has already changed since v1.2 (v1.2 MPI_MAX_PORT_NAME
    == 36).  Hence, this commit simply increases the value from a
    previous change.
 1. The changes does increase OMPI's memory footprint slightly, but
    only when using MPI-2 dynamics.  So it is expected that the change
    will have minimal impact on the overall footprint.
 1. The change is helpful for nodes that have 4 or more IP networks
    (e.g., regular ethernet and multiple IP-over-<pick your favorite
    high-speed network> networks).  Without this change, invoking
    MPI_COMM_SPAWN on hosts with 4 or more IP networks will fail
    because we'll exceed 256 bytes for the port name.  Some OMPI
    developer test clusters already have this kind of configuration
    (e.g., Cisco); it is expected that this is not too common in the
    real world yet, but with "manycore" coming, having multiple
    IP-based networks in a single server will likely become more
    common.

This commit was SVN r19638.

ompi/include/mpi.h.in

@@ -290,7 +290,7 @@ typedef int (MPI_Grequest_cancel_function)(void *, int);
 #define MPI_ARGV_NULL            ((char **) 0)   /* NULL argument vector */
 #define MPI_ARGVS_NULL           ((char ***) 0)  /* NULL argument vectors */
 #define MPI_ERRCODES_IGNORE      ((int *) 0)    /* don't return error codes */
-#define MPI_MAX_PORT_NAME        256     /* max port name length */
+#define MPI_MAX_PORT_NAME        1024    /* max port name length */
 #define MPI_MAX_NAME_LEN         MPI_MAX_PORT_NAME /* max port name length */
 #define MPI_ORDER_C              0       /* C row major order */
 #define MPI_ORDER_FORTRAN        1       /* Fortran column major order */