Add extended command #kick

I've seen some complaints about not being able to kick with ^d
so add kick as an extended command.

Also add the missing #exploremode command to the Guidebook.

doc/Guidebook.mn

@@ -860,12 +860,16 @@ See the section below entitled ``Conduct'' for details.
 Dip an object into something.
 .lp #enhance
 Advance or check weapon and spell skills.
+.lp #exploremode
+Enter the explore mode.
 .lp #force
 Force a lock.
 .lp #invoke
 Invoke an object's special powers.
 .lp #jump
 Jump to another location.
+.lp #kick
+Kick something.
 .lp #loot
 Loot a box or bag on the floor beneath you, or the saddle 
 from a steed standing next to you.

doc/Guidebook.tex

@@ -1042,6 +1042,9 @@ Dip an object into something.
 \item[\tb{\#enhance}]
 Advance or check weapon and spell skills.
 %.lp
+\item[\tb{\#exploremode}]
+Enter the explore mode.
+%.lp
 \item[\tb{\#force}]
 Force a lock.
 %.lp
@@ -1051,6 +1054,9 @@ Invoke an object's special powers.
 \item[\tb{\#jump}]
 Jump to another location.
 %.lp
+\item[\tb{\#kick}]
+Kick something.
+%.lp
 \item[\tb{\#loot}]
 Loot a box or bag on the floor beneath you, or the saddle 
 from a steed standing next to you.

src/cmd.c

@@ -2777,6 +2777,7 @@ struct ext_func_tab extcmdlist[] = {
     { "force", "force a lock", doforce, FALSE },
     { "invoke", "invoke an object's powers", doinvoke, TRUE },
     { "jump", "jump to a location", dojump, FALSE },
+    { "kick", "kick something", dokick, FALSE },
     { "loot", "loot a box on the floor", doloot, FALSE },
     { "monster", "use a monster's special ability", domonability, TRUE },
     { "name", "name a monster or an object", docallcmd, TRUE },