pcre: use PCRE_NO_UTF8_CHECK properly

In order to obtain the behavior we want, i.e., to disable
error-on-invalid-UTF-in-input, apply this PCRE option in
pcre_exec, not when compiling.
* src/pcresearch.c (Pexecute): Use PCRE_NO_UTF8_CHECK here, ...
(Pcompile): ...rather than here.
* tests/pcre-invalid-utf8-input: Adjust test case to test for this.
gnulib: update to latest
maint: update copyright dates for 2014

Do that by running "make update-copyright".
gnulib: update to latest, for maint.mk fix
version 2.16

* NEWS: Record release date.
maint: post-release administrivia

* NEWS: Add header line for next release.
* .prev-version: Record previous version.
* cfg.mk (old_NEWS_hash): Auto-update.