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>

include/config_cmd_default.h

@@ -16,7 +16,6 @@
  * hardware, not fully tested, etc.).
  */
 
-#define CONFIG_CMD_AUTOSCRIPT	/* Autoscript Support		*/
 #define CONFIG_CMD_BDI		/* bdinfo			*/
 #define CONFIG_CMD_BOOTD	/* bootd			*/
 #define CONFIG_CMD_CONSOLE	/* coninfo			*/
@@ -37,6 +36,7 @@
 #define CONFIG_CMD_NFS		/* NFS support			*/
 #define CONFIG_CMD_RUN		/* run command in env variable	*/
 #define CONFIG_CMD_SETGETDCR	/* DCR support on 4xx		*/
+#define CONFIG_CMD_SOURCE	/* "source" command support	*/
 #define CONFIG_CMD_XIMG		/* Load part of Multi Image	*/
 
 #endif	/* _CONFIG_CMD_DEFAULT_H */