Fix MULTIPLE-VALUE-BIND when binding special variables.
Fix MULTIPLE-VALUE-BIND when binding special variables.

M-V-B on special variables gets converted to M-V-B on lexical variables,
which are then used to let-bind the original special variables.
The use counts on these lexical variables were not being set correctly
and they were being incorrectly removed.

froggey/Mezzano,rvedam/Mezzano,rvedam/Mezzano,froggey/Mezzano,varjagg/Mezzano,varjagg/Mezzano,AugustusHuang/Mezzano,AugustusHuang/Mezzano