Prevent walking into water or lava by default

Make paranoid_confirmation:swim the default, because it is far more
beginner friendly.

doc/Guidebook.mn

@@ -4103,7 +4103,7 @@ symbols for the various object types.
 Any omitted types are filled in at the end from the previous order.
 .lp paranoid_confirmation
 A space separated list of specific situations where alternate
-prompting is desired.  The default is paranoid_confirmation:pray.
+prompting is desired.  The default is \(lqparanoid_confirmation:pray swim\(rq.
 .PS Were-change
 .PL Confirm
 for any prompts which are set to require \(lqyes\(rq rather than \(oqy\(cq,

doc/Guidebook.tex

@@ -4489,7 +4489,7 @@ are filled in at the end from the previous order.
 %.lp
 \item[\ib{paranoid\verb+_+confirmation}]
 A space separated list of specific situations where alternate
-prompting is desired.  The default is ``{\it paranoid\verb+_+confirmation:pray}''.
+prompting is desired.  The default is ``{\it paranoid\verb+_+confirmation:pray swim}''.
 %.sd
 %.si
 \newlength{\pcwidth}

src/options.c

@@ -6085,7 +6085,7 @@ initoptions_init(void)
     flags.end_own = FALSE;
     flags.end_top = 3;
     flags.end_around = 2;
-    flags.paranoia_bits = PARANOID_PRAY; /* old prayconfirm=TRUE */
+    flags.paranoia_bits = PARANOID_PRAY|PARANOID_SWIM;
     flags.pile_limit = PILE_LIMIT_DFLT;  /* 5 */
     flags.runmode = RUN_LEAP;
     iflags.msg_history = 20;