Updating level 1 commands.

exit - correctly convert the parameter to the return code.
for  - update string-to-number conversion.
if   - use shell string-to-number conversion and add comments.
stall- add command

main lib files:
add comments, clarify user visible strings, add stall.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@11420 6f19259b-4bc3-4df7-8a09-765794883524

ShellPkg/Library/UefiShellLevel1CommandsLib/UefiShellLevel1CommandsLib.inf

@@ -1,7 +1,7 @@
 ##  @file
 #  Provides shell level 1 functions
 #
-#  Copyright (c) 2009-2010, Intel Corporation. All rights reserved. <BR>
+#  Copyright (c) 2009-2011, Intel Corporation. All rights reserved. <BR>
 #
 #  This program and the accompanying materials
 #  are licensed and made available under the terms and conditions of the BSD License
@@ -31,6 +31,7 @@
   If.c
   For.c
   Shift.c
+  Stall.c
 
 [Packages]
   MdePkg/MdePkg.dec