Fix an amusing typo that completely the re-introduction of parameters

for the purposes of parsing default arguments. In effect, we would
re-introduce the parameter with a default argument N times (where N is
the number of parameters preceding the parameter with a default
argument). This showed up when a defaulted parameter of a member
function of a local class shadowed a parameter of the enclosing
function. Fixes PR6383.

llvm-svn: 97534