Add paranoid:swim to prevent typoing into water or lava

In the name of accessibility: Prevent moving into dangerous liquids.

Now with themed rooms, water and lava are more common, and it's
unreasonable to expect blind players to check every step for those.
With paranoid:swim, just prevent normal walking into those liquids,
unless you prefix the movement with 'm', or if the liquid would not
harm you.

Doesn't completely prevent an accidental dunking - for example
if the hero is impaired or couldn't see the liquid.

This comes from xNetHack by copperwater <aosdict@gmail.com>
with some changes to the code.

doc/Guidebook.tex

@@ -4430,6 +4430,8 @@ than immediately praying; on by default;
 \item[{\tt Remove~}] require selection from inventory for `{\tt R}'
 and `{\tt T}'
 commands even when wearing just one applicable item.
+\item[{\tt swim~~~}]
+prevent walking into water or lava.
 \item[{\tt all~~~~}]
 turn on all of the above.
 \elist
@@ -6054,6 +6056,9 @@ A lot of speech access programs use the number-pad to review the screen.
 If this is the case, disable the number\verb+_+pad option and use the
 traditional Rogue-like commands.
 %.lp
+\item[\ib{paranoid\verb+_+confirmation:swim}]
+Prevent walking into water or lava.
+%.lp
 \item[\ib{autodescribe}]
 Automatically describe the terrain under the cursor when targeting.
 %.lp