Restful sleep gives a warning message

doc/fixes3-7-0.txt

@@ -324,6 +324,7 @@ hero poly'd into rust monster could implicitly eat bars when adjacent by
 	can explicitly eat them via 'e' after moving onto their spot
 monster hiding under an egg that hatched was kept hidden
 restful sleep regenerates hit points
+restful sleep gives a warning message few turns before you fall asleep
 attacking non-adjacent concealed mimic by applying a polearm would make the
 	hero be stuck to that mimic
 hero could break a wand ("raising the wand high over your head, you break it

src/timeout.c

@@ -7,6 +7,7 @@
 
 static void stoned_dialogue(void);
 static void vomiting_dialogue(void);
+static void sleep_dialogue(void);
 static void choke_dialogue(void);
 static void levitation_dialogue(void);
 static void slime_dialogue(void);
@@ -258,6 +259,15 @@ vomiting_dialogue(void)
     exercise(A_CON, FALSE);
 }
 
+static void
+sleep_dialogue(void)
+{
+    long i = (HSleepy & TIMEOUT);
+
+    if (i == 4)
+        You("yawn.");
+}
+
 DISABLE_WARNING_FORMAT_NONLITERAL   /* RESTORE is after slime_dialogue */
 
 static NEARDATA const char *const choke_texts[] = {
@@ -590,6 +600,8 @@ nh_timeout(void)
         levitation_dialogue();
     if (HPasses_walls & TIMEOUT)
         phaze_dialogue();
+    if (HSleepy & TIMEOUT)
+        sleep_dialogue();
     if (u.mtimedone && !--u.mtimedone) {
         if (Unchanging)
             u.mtimedone = rnd(100 * gy.youmonst.data->mlevel + 1);