Implement the sleep() function and make both sleep() and usleep() public. Required initially for Python, but these functions have general applicability. Signed-off-by: duanev@gmail.com Reviewed-by: darylm503 git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@12323 6f19259b-4bc3-4df7-8a09-765794883524