unbind

# File ext/dl/lib/dl/func.rb, line 120
    def unbind()
      if( @cfunc.ptr != 0 )
        case @cfunc.calltype
        when :cdecl
          remove_cdecl_callback(@cfunc.ptr, @cfunc.ctype)
        when :stdcall
          remove_stdcall_callback(@cfunc.ptr, @cfunc.ctype)
        else
          raise(RuntimeError, "unsupported calltype: #{@cfunc.calltype}")
        end
        @cfunc.ptr = 0
      end
    end