...(according to
<http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1579> it is fixed
in C++14), but for safety, leave the configure.ac check in for some longer.

Change-Id: Ibd2f0cac228117e35ac299e2fe74207394c900cd
Reviewed-on: https://gerrit.libreoffice.org/64773
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>