12310 Add demangle(1) command

@@ -12,10 +12,11 @@
 #
 # Copyright 2011, Richard Lowe
 # Copyright 2018 Nexenta Systems, Inc.
 # Copyright 2014 Garrett D'Amore <garrett@damore.org>
 # Copyright 2019 OmniOS Community Edition (OmniOSce) Association.
+# Copyright 2020 Joyent, Inc.
 #
 
 include         $(SRC)/Makefile.master
 
 MANSECT=        1

@@ -92,10 +93,11 @@
                 ctwatch.1                       \
                 cut.1                           \
                 date.1                          \
                 dc.1                            \
                 deallocate.1                    \
+                demangle.1                      \
                 deroff.1                        \
                 dhcpinfo.1                      \
                 diff.1                          \
                 diff3.1                         \
                 diffmk.1                        \