Use static buffers for mprintf and debug_printf, cut down on library dependencies

mailtest/Makefile

@@ -2,7 +2,6 @@ include ../make/ufuncs.mk
 
 $(eval $(call add_lib,libprocess))
 $(eval $(call add_lib,libstring))
-$(eval $(call add_lib,libmalloc))
 $(eval $(call add_lib,libdebugconsole))
 $(eval $(call add_lib,libaux))
 

mailtest/mailtest.c

@@ -23,10 +23,11 @@ void app_main (void) {
     char recv_buffer[1024];
 
     for (;;) {
+      debug_printf ("Waiting...\n");
       memset (recv_buffer, 0, sizeof (recv_buffer));
       mail_receive (recv_buffer, sizeof (recv_buffer));
 
-      debug_printf ("%s\n", recv_buffer);
+      debug_printf ("Recv: %s\n", recv_buffer);
     }
   } else if (strcmp (commandbuf, "send") == 0) {
     if (env_get (process_get_pgid (), "payload", (void*)payloadbuf, sizeof (payloadbuf)) != ST_OK) {