Use the MPI-2 communicator error-handler API retained by MPI-3, fix the format
used for the queue's size_t length, and make shared globals compatible with
GCC's -fno-common default.

--- a/src/hre-mpi/hre_mpi.c
+++ b/src/hre-mpi/hre_mpi.c
@@ -424,7 +424,7 @@ mpi_start(int *argc_p,char **argv_p[],int me,int peers){
     } else {
         MPI_Init(argc_p,argv_p);
     }
-    MPI_Errhandler_set(MPI_COMM_WORLD,MPI_ERRORS_ARE_FATAL);
+    MPI_Comm_set_errhandler(MPI_COMM_WORLD,MPI_ERRORS_ARE_FATAL);
     hre_context_t ctx=HREctxMPI(MPI_COMM_WORLD);
     HREmainSet(ctx);
     HREglobalSet(ctx);
--- a/src/hre-mpi/mpi_event_loop.c
+++ b/src/hre-mpi/mpi_event_loop.c
@@ -28 +28 @@ void event_statistics(log_t log,event_queue_t queue){
-    Print(log,"queue size is %d",array_size(queue->man));
+    Print(log,"queue size is %zu",array_size(queue->man));
--- a/src/ce/Dtaudlts.c
+++ b/src/ce/Dtaudlts.c
@@ -41 +41 @@ int* totsize;
-int me, nodes;
+extern int me, nodes;