Prettified and hardened string/backslash quoting with ipsystem(), ipalias() and ...
Prettified and hardened string/backslash quoting with ipsystem(), ipalias() and
ipmagic(). Now even \ characters are passed to %magics, !shell escapes and aliases
exactly as they are in the ipython command line.
Still have to fix cd to accept backslashes in windows, maybe by removing
parse_options...
