Add signal documentation from Kurt Lidl @ FreeBSD

s/don't/do not/

external/bsd/blacklist/bin/blacklistd.8

@@ -1,4 +1,4 @@
-.\" $NetBSD: blacklistd.8,v 1.18 2016/07/30 06:09:29 dholland Exp $
+.\" $NetBSD: blacklistd.8,v 1.19 2019/11/06 20:29:46 christos Exp $
 .\"
 .\" Copyright (c) 2015 The NetBSD Foundation, Inc.
 .\" All rights reserved.
@@ -27,7 +27,7 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd June 7, 2016
+.Dd November 6, 2019
 .Dt BLACKLISTD 8
 .Os
 .Sh NAME
@@ -178,7 +178,7 @@ Specify the default rule name for the packet filter rules, usually
 .It Fl r
 Re-read the firewall rules from the internal database, then
 remove and re-add them.
-This helps for packet filters that don't retain state across reboots.
+This helps for packet filters that do not retain state across reboots.
 .It Fl s Ar sockpath
 Add
 .Ar sockpath
@@ -197,6 +197,26 @@ diagnostic messages to
 .Dv stdout
 instead of
 .Xr syslogd 8 .
+.Sh SIGNAL HANDLING
+.Nm
+deals with the following signals:
+.Bl -tag -width "USR2"
+.It HUP
+Receipt of this signal causes
+.Nm
+to re-read the configuration file.
+.It INT, TERM & QUIT
+These signals tell
+.Nm
+to exit in an orderly fashion.
+.It USR1
+This signal tells
+.Nm
+to increase the internal debugging level by 1.
+.It USR2
+This signal tells
+.Nm
+to decrease the internal debugging level by 1.
 .El
 .Sh FILES
 .Bl -tag -width /libexec/blacklistd-helper -compact