Add "source" command; prepare removal of "autoscr" command

According to the doc/feature-removal-schedule.txt, the "autoscr"
command will be replaced by the "source" command in approximately 6
months from now.

This patch prepares this change and starts a 6 month transition
period as follows:

- The new "source" command has been added, which implements exactly
  the same functionlaity as the old "autoscr" command before
- The old "autoscr" command name is kept as an alias for compatibility
- Command sequences, script files atc. have been adapted to use the
  new "source" command
- Related environment variables ("autoscript", "autoscript_uname")
  have *not* been adapted yet; these will be renamed resp. removed in
  a separate patch when the support for the "autoscr" command get's
  finally dropped.

Signed-off-by: Wolfgang Denk <wd@denx.de>

common/cmd_net.c

@@ -222,9 +222,10 @@ netboot_common (proto_t proto, cmd_tbl_t *cmdtp, int argc, char *argv[])
 		rcode = do_bootm (cmdtp, 0, 1, local_args);
 	}
 
-#ifdef CONFIG_AUTOSCRIPT
+#ifdef CONFIG_SOURCE
 	if (((s = getenv("autoscript")) != NULL) && (strcmp(s,"yes") == 0)) {
-		printf ("Running autoscript at addr 0x%08lX", load_addr);
+		printf ("Running "source" command at addr 0x%08lX",
+			load_addr);
 
 		s = getenv ("autoscript_uname");
 		if (s)
@@ -233,7 +234,7 @@ netboot_common (proto_t proto, cmd_tbl_t *cmdtp, int argc, char *argv[])
 			puts (" ...\n");
 
 		show_boot_progress (83);
-		rcode = autoscript (load_addr, s);
+		rcode = source (load_addr, s);
 	}
 #endif
 	if (rcode < 0)