Define std::fpos special members as defaulted

	* include/bits/postypes.h (fpos): Define special members as defaulted.

From-SVN: r261156

libstdc++-v3/ChangeLog

 2018-06-04  Jonathan Wakely  <jwakely@redhat.com>
 
+	* include/bits/postypes.h (fpos): Define special members as defaulted.
+
 	PR libstdc++/85930
 	* include/bits/shared_ptr_base.h (_Sp_make_shared_tag::_S_ti): Align
 	the static variable correctly.

libstdc++-v3/include/bits/postypes.h

@@ -133,6 +133,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       fpos(streamoff __off)
       : _M_off(__off), _M_state() { }
 
+#if __cplusplus >= 201103L
+      fpos(const fpos&) = default;
+      fpos& operator=(const fpos&) = default;
+      ~fpos() = default;
+#endif
+
       /// Convert to streamoff.
       operator streamoff() const { return _M_off; }