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/atstk1002.h b/include/configs/atstk1002.h
index 2284277..b258f2d 100644
--- a/include/configs/atstk1002.h
+++ b/include/configs/atstk1002.h
@@ -142,9 +142,9 @@
 #define CONFIG_CMD_JFFS2
 #define CONFIG_CMD_MMC
 
-#undef CONFIG_CMD_AUTOSCRIPT
 #undef CONFIG_CMD_FPGA
 #undef CONFIG_CMD_SETGETDCR
+#undef CONFIG_CMD_SOURCE
 #undef CONFIG_CMD_XIMG
 
 #define CONFIG_ATMEL_USART		1