Log Message:
Update ZoneMinder from 1.25.0 to 1.28.1.

Numerous changes, documented at:
 https://github.com/ZoneMinder/ZoneMinder/releases

Addresses two security advisories:

  https://github.com/ZoneMinder/ZoneMinder/releases/tag/v1.28.0
  http://secunia.com/advisories/62918/

Pkgsrc changes:

patch-src_zm_signal_h is no longer necessary because zm_signal.h uses
HAVE_EXECINFO_H.

patch-src_zmf_cpp appears to be applied upstream.

patch-configure_ac no longer needs to set PATH_BUILD to
PREFIX/share/zoneminder, so that zmupdate.pl can locate the database build
scripts as installed files.  Upstream has now implemented this via the
ZM_PATH_DATA entry in zm.conf, and adds a ZM_PATH_DATA/db subdirectory.

src/Makefile.am no longer setuid's zmfix, as zmfix was removed from
ZoneMinder 1.26.6.

The code now uses clock_gettime(), which on some systems (like Linux), calls
for -lrt.  Since the build system isn't aware of this, but Pkgsrc is, just set
PTHREAD_AUTO_VARS=yes.

The PHP code now uses PDO for DB access, but it looks like there are some
straggling dependencies on the raw MySQL driver, so both are pulled in.