@codequote* commands

[Eli Zaretskii]

These commands are new in Texinfo 5.0 and later, and cause errors in
4.x series.  The corresponding "@set txicodequote*" variables, which
are available since v4.11, are only hinted at in the Texinfo manual:

    This feature used to be controlled by '@set' variable names; they are
  still supported, but the command interface is preferred.

Why aren't the variable names mentioned explicitly in the manual?  If
a manual needs to be acceptable to both v4.x and v5.x series
(something that still happens quite a lot, given the slow speed of
makeinfo 5.x), the authors will have hard time discovering those
variables' names.

Is it OK to mention the variables as well, or are they omitted on
purpose?