don't include empty substitutions in simplifier, replace variable of case of variable with the default binding when possible
don't include empty substitutions in simplifier, replace variable of case of variable with the default binding when possible

darcs-hash:20060420030530-1a7c6-3d67729fbf12474f57e4f8814d8994dac33815cf

jimcrayne/jhc,jimcrayne/jhc,jimcrayne/jhc,jimcrayne/jhc