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_all.h

@@ -15,7 +15,6 @@
 
 #define CONFIG_CMD_AMBAPP	/* AMBA Plug & Play Bus print utility */
 #define CONFIG_CMD_ASKENV	/* ask for env variable		*/
-#define CONFIG_CMD_AUTOSCRIPT	/* Autoscript Support		*/
 #define CONFIG_CMD_BDI		/* bdinfo			*/
 #define CONFIG_CMD_BEDBUG	/* Include BedBug Debugger	*/
 #define CONFIG_CMD_BMP		/* BMP support			*/
@@ -76,6 +75,7 @@
 #define CONFIG_CMD_SETEXPR	/* setexpr support		*/
 #define CONFIG_CMD_SETGETDCR	/* DCR support on 4xx		*/
 #define CONFIG_CMD_SNTP		/* SNTP support			*/
+#define CONFIG_CMD_SOURCE	/* "source" command support	*/
 #define CONFIG_CMD_SPI		/* SPI utility			*/
 #define CONFIG_CMD_TERMINAL	/* built-in Serial Terminal	*/
 #define CONFIG_CMD_UNIVERSE	/* Tundra Universe Support	*/