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/include/configs/at91sam9263ek.h b/include/configs/at91sam9263ek.h
index dd500ca..78e0081 100644
--- a/include/configs/at91sam9263ek.h
+++ b/include/configs/at91sam9263ek.h
@@ -91,11 +91,11 @@
  */
 #include <config_cmd_default.h>
 #undef CONFIG_CMD_BDI
-#undef CONFIG_CMD_IMI
-#undef CONFIG_CMD_AUTOSCRIPT
 #undef CONFIG_CMD_FPGA
-#undef CONFIG_CMD_LOADS
+#undef CONFIG_CMD_IMI
 #undef CONFIG_CMD_IMLS
+#undef CONFIG_CMD_LOADS
+#undef CONFIG_CMD_SOURCE
 
 #define CONFIG_CMD_PING		1
 #define CONFIG_CMD_DHCP		1