doc/drop.log: mark as deprecated and scheduled to be removed

Also make sure options are in sync with those in
suricata.yaml.

doc/userguide/configuration/suricata-yaml.rst

@@ -583,6 +583,9 @@ With this option it is possible to send all alert and event output to syslog.
 Drop.log, a line based information for dropped packets
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
+.. note:: This output has been deprecated and will be removed by
+          June 2020.
+
 If Suricata works in IPS mode, it can drop packets based on
 rules. Packets that are being dropped are saved in the drop.log file,
 a Netfilter log format.
@@ -592,8 +595,11 @@ a Netfilter log format.
   - drop:
        enabled: yes              #The option is enabled.
        filename: drop.log        #The log-name of the file for dropped packets.
-       append: yes               #If this option is set to yes, the last filled drop.log-file will not be
-                                  #overwritten while restarting Suricata. If set to 'no' the last filled drop.log file will be overwritten.
+       append: yes               #If this option is set to yes, the last filled
+                                 #drop.log-file will not be overwritten while
+                                 #restarting Suricata. If set to 'no' the last
+                                 #filled drop.log file will be overwritten.
+       filetype: regular         #regular, unis_stream, unix_dgram
 
 .. _suricata-yaml-file-store: