Recognize a "pureftpd_flags" variable in pure-ftpd's rc script. Pretty much
anything that can be placed in /usr/local/etc/pure-ftpd.conf can be placed in
this variable instead.
ftp/pure-ftpd/Makefile
Bump PORTREVISION
ftp/pure-ftpd/files/pure-ftpd.in
Handle pureftpd_flags. It needs special handling because, unlike most
daemons, pure-config.pl takes its mandatory argument first and its
optional flags last.