Document how to escape keywords with simple quotes.
Document how to escape keywords with simple quotes.

	* doc/specs/urbi-specs.tex: Here.

urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,aldebaran/urbi,aldebaran/urbi,aldebaran/urbi,urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,aldebaran/urbi,aldebaran/urbi,aldebaran/urbi,aldebaran/urbi,aldebaran/urbi