Implement proper linkage for explicit instantiation declarations of

inlined functions. For example, given

  template<typename T>
  class string {
    unsigned Len;

  public:
    unsigned size() const { return Len; }
  };

  extern template class string<char>;

we now give the instantiation of string<char>::size
available_externally linkage (if it is ever instantiated!), as
permitted by the C++0x standard.
      

llvm-svn: 85340