fix U88 - invisible hero didn't sense self via ESP

If the character was invisible without being able to see invisible,
his location on the map showed any object there or underlying topology
instead of the hero even when monsters could be seen with infravision,
ESP, or sustained monster detection.  The ESP case required an amulet
or helm or quest artifact to be noticeable because being blind overrides
being unable to see invisible, so the more common form of telepathy
didn't exhibit this behavior.

include/display.h

@@ -125,6 +125,7 @@
 
 /*
  * canseeself()
+ * senseself()
  *
  * This returns true if the hero can see her/himself.
  *
@@ -132,7 +133,8 @@
  * invisible.  If not, then we don't need the check.
  */
 #define canseeself()	(Blind || u.uswallow || (!Invisible && !u.uundetected))
-
+#define senseself()	(canseeself() || Infravision || Unblind_telepat || \
+			 Detect_monsters)
 
 /*
  * random_monster()
@@ -192,28 +194,22 @@
  * _if_ the hero can be seen have already been done.
  */
 #ifdef STEED
-#define display_self()							\
-    show_glyph(u.ux, u.uy,						\
-	(u.usteed && mon_visible(u.usteed)) ?			\
-				ridden_mon_to_glyph(u.usteed) :		\
-	youmonst.m_ap_type == M_AP_NOTHING ?				\
-				hero_glyph :					\
-	youmonst.m_ap_type == M_AP_FURNITURE ?				\
-				cmap_to_glyph(youmonst.mappearance) :	\
-	youmonst.m_ap_type == M_AP_OBJECT ?				\
-				objnum_to_glyph(youmonst.mappearance) : \
-	/* else M_AP_MONSTER */ monnum_to_glyph(youmonst.mappearance))
+#define maybe_display_usteed	(u.usteed && mon_visible(u.usteed)) ? \
+					ridden_mon_to_glyph(u.usteed) :
 #else
+#define maybe_display_usteed	/* empty */
+#endif
+
 #define display_self()							\
     show_glyph(u.ux, u.uy,						\
+	maybe_display_usteed			/* else */		\
 	youmonst.m_ap_type == M_AP_NOTHING ?				\
-				hero_glyph :					\
+				hero_glyph :				\
 	youmonst.m_ap_type == M_AP_FURNITURE ?				\
 				cmap_to_glyph(youmonst.mappearance) :	\
 	youmonst.m_ap_type == M_AP_OBJECT ?				\
 				objnum_to_glyph(youmonst.mappearance) : \
 	/* else M_AP_MONSTER */ monnum_to_glyph(youmonst.mappearance))
-#endif
 
 /*
  * A glyph is an abstraction that represents a _unique_ monster, object,