Proposed resolution:

In [filebuf]/5 change the "as if" code

const codecvt<charT,char,typename traits::state_type>& a_codecvt =
  use_facet<codecvt<charT,char,typename traits::state_type> >(getloc());

In [facet.num.put.virtuals]/15 (This is para 5 in N2134) change

A local variable punct is initialized via

const numpunct<charT>& punct = use_facet< numpunct<charT> >(str.getloc() );

(Please note also the additional provided trailing semicolon)