issue #1027 - sticky 'nofollowers' flag

Reported by copperwater:  entering the tutorial sets 'u.nofollowers',
changing to the tutorial level saves a copy of 'u', post-level change
from entering the tutorial level resets u.followers, but subsequently
changing levels to return to the original level 1 restores 'u' from
the saved copy with has 'u.nofollowers==True', overriding the reset.

Move the nofollowers flag from 'u' to 'iflags'.  Invalides save and
bones files.

Fixes #1027

include/flag.h

@@ -197,6 +197,7 @@ struct instance_flags {
     boolean invis_goldsym; /* gold symbol is ' '? */
     boolean in_lua;        /* executing a lua script */
     boolean lua_testing;   /* doing lua tests */
+    boolean nofollowers;   /* level change ignores pets (for tutorial) */
     boolean partly_eaten_hack; /* extra flag for xname() used when it's called
                                 * indirectly so we can't use xname_flags() */
     boolean remember_getpos; /* save getpos() positioning in do-again queue */

include/patchlevel.h

@@ -17,7 +17,7 @@
  * Incrementing EDITLEVEL can be used to force invalidation of old bones
  * and save files.
  */
-#define EDITLEVEL 85
+#define EDITLEVEL 86
 
 /*
  * Development status possibilities.

include/you.h

@@ -358,7 +358,6 @@ struct you {
     d_level utolev;     /* level monster teleported you to, or uz */
     uchar utotype;      /* bitmask of goto_level() flags for utolev */
     d_level ucamefrom;  /* level where you came from; used for tutorial */
-    boolean nofollowers; /* level change ignores monster followers/pets */
     boolean umoved;     /* changed map location (post-move) */
     int last_str_turn;  /* 0: none, 1: half turn, 2: full turn
                          * +: turn right, -: turn left */