add some new, easier achievements

Introduce eight achievements that can be attained by more players.
 Entered Gnomish Mines  - self explanatory
 Entered Mine Town      - the town portion, not just the level
 Entered a shop         - any tended shop on any level
 Entered a temple       - likewise for temple
 Consulted the Oracle   - bought at least one major or minor oracle
 Read a Discworld Novel - read at least one passage
 Entered Sokoban        - like mines
 Entered the Big Room   - not always possible since not always present

The novel and bigroom ones aren't always achieveable since novels are
only guaranteed if a book or scroll shop gets created and bigroom is
only guaranteed in wizard mode.  No one ever claimed that every
possible achievement can be attained in a single game.  (If one for
entering the Fort Ludios level--or perhaps entering the Fort itself--
eventually gets add, that won't be possible in every game either.)

The mine town one probably needs some tweaking.  Two of the town's
seven variants have no town boundary (despite a rectangular area of
pre-defined map) and at present simply arriving on either of those
levels is enough to be credited with the entered-town achievement.

Bump EDITLEVEL because u.uachieved[] has increased in size.  This
time it has been expanded to the maximum that xlogfile's bitmask of
achievements can handle, enough for up to 9 more achievements without
another EDITLEVEL increment.

include/context.h

@@ -106,8 +106,10 @@ struct novel_tracking { /* for choosing random passage when reading novel */
 };
 
 struct achievement_tracking {
-    unsigned mines_prize_oid, soko_prize_oid; /* obj->o_id */
-    /* short mines_prize_type, soko_prize_typ1, soko_prize_typ2; */
+    unsigned mines_prize_oid,  /* luckstone->o_id */
+             soko_prize_oid,   /* {bag or amulet}->o_id */
+             castle_prize_old; /* wand->o_id; not yet implemented */
+    boolean minetn_reached;    /* avoid redundant checking for town entry */
 };
 
 struct context_info {