query-replace-regexp: Can't use \0 in TO-STRING

[zhanghj]

The doc says:
In TO-STRING, ‘\&’ or ‘\0’ stands for whatever matched the whole of
REGEXP, and ‘\N’ (where N is a digit) stands for whatever matched
the Nth ‘\(...\)’ (1-based) in REGEXP.  The ‘\(...\)’ groups are
counted from 1.

But when using \0, emacs gives the following error message: 
match-substitute-replacement: Invalid use of ‘\’ in replacement text

Using \& is OK.