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.

include/mondata.h

@@ -38,6 +38,7 @@
 #define is_floater(ptr) ((ptr)->mlet == S_EYE || (ptr)->mlet == S_LIGHT)
 /* clinger: piercers, mimics, wumpus -- generally don't fall down holes */
 #define is_clinger(ptr) (((ptr)->mflags1 & M1_CLING) != 0L)
+#define grounded(ptr) (!is_flyer(ptr) && !is_floater(ptr) && !is_clinger(ptr))
 #define is_swimmer(ptr) (((ptr)->mflags1 & M1_SWIM) != 0L)
 #define breathless(ptr) (((ptr)->mflags1 & M1_BREATHLESS) != 0L)
 #define amphibious(ptr) \