Optimize "emit ev ~ inf".
Optimize "emit ev ~ inf".

	* src/rewrite/desugarer.cc (visit (const ast::Emit*)): Do not
	schedule a background task if it has work to do only at the
	end of times. Also narrow the scope of the temporary declarations
	so that this construct can be used several times in the same
	scope.

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