Match type names and give more info for out-of-line function definition errors.

Having a function declaration and definition with different types for a
parameter where the types have same (textual) name can occur when an unqualified
type name resolves to types in different namespaces in each location.

The error messages have been extended by adding notes that point to the first
parameter of the function definition that doesn't match the declaration, instead
of a generic "member declaration nearly matches". The generic message is still
used in cases where the mismatch is not in the paramenter list, such as
mismatched cv qualifiers on the member function itself.

llvm-svn: 136891