bug#13704: Typo in Emacs Lisp manual, Minor Mode Conventions

[Mariano Street]

I have found a typo in the Minor Mode Conventions section of the Emacs
Lisp manual.  The first list item says:

     The value will be `nil' is the mode is disabled, and non-`nil' if
     the mode is enabled.

The first `is' should be `if' instead.

My version of GNU Emacs is 24.2.1, although the error is currently
present in trunk: 
http://bzr.savannah.gnu.org/lh/emacs/trunk/annotate/head:/doc/lispref/modes.texi