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>
diff --git a/board/cray/L1/L1.c b/board/cray/L1/L1.c
index 1c82bdf..8a06ecc 100644
--- a/board/cray/L1/L1.c
+++ b/board/cray/L1/L1.c
@@ -164,7 +164,7 @@
 			setenv ("ethaddr", e);
 		}
 	}
-	sprintf (bootcmd,"autoscript %X",(unsigned)bootscript);
+	sprintf (bootcmd,"source %X",(unsigned)bootscript);
 	setenv ("bootcmd", bootcmd);
 	return (0);
 }