When instantiating function definitions set parameter names to those used in template
When instantiating function definitions set parameter names to those used in template

The rationale is that we are copying the entire definition including
parameter names which may differ between the declaration and the
definition.

This is particularly important if any parameters are unnamed in the
declaration, as a DeclRef to an unnamed ParmVarDecl would cause the
pretty printer to produce invalid output.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@108643 91177308-0d34-0410-b5e6-96231b3b80d8

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