bug#4848: 23.1.50; \u and \x in string

[Richard Stallman <rms@gnu.org>]

    I'm not sure what you wanted to be documented.  Is the description in
    "(elisp)General Escape Syntax" what you were looking for?

The version I have is from August.  If it has been substantially
improved since then, maybe it is good.  The text from August was
inadequate and even wrong:

      To use hex, write a question mark followed by a backslash, @samp{x},
    and the hexadecimal character code.  You can use any number of hex
    digits, so you can represent any character code in this way.
    Thus, @samp{?\x41} for the character @kbd{A}, @samp{?\x1} for the
    character @kbd{C-a}, and @code{?\x8e0} for the Latin-1 character
    @iftex
    @samp{@`a}.
    @end iftex
    @ifnottex
    @samp{a} with grave accent.
    @end ifnottex

And here is something from Non-ASCII In Strings:

      You can also represent a multibyte non-@acronym{ASCII} character with its
    character code: use a hex escape, @samp{\x@var{nnnnnnn}}, with as many
    digits as necessary.  (Multibyte non-@acronym{ASCII} character codes are all
    greater than 256.)  Any character which is not a valid hex digit
    terminates this construct.  If the next character in the string could be
    interpreted as a hex digit, write @w{@samp{\ }} (backslash and space) to
    terminate the hex escape---for example, @w{@samp{\x8e0\ }} represents
    one character, @samp{a} with grave accent.  @w{@samp{\ }} in a string
    constant is just like backslash-newline; it does not contribute any
    character to the string, but it does terminate the preceding hex escape.