Chronicle of major events, and livelog

Log game events, such as entering a new dungeon level, breaking
a conduct, or killing a unique monster, in a new "Major events"
chronicle. The entries record the turn when the event happened.
The log can be viewed with #chronicle -command, and the entries
also show up in the end-of-game dump, if that is available.

This feature is on by default, but can be disabled by
defining NO_CHRONICLE compile-time option.

This also contains "live logging", writing the events as they
happen into a single livelog-file. This is mostly useful for
public servers. The livelog is off by default, and must be
compiled in with LIVELOG, and then turned on in sysconf.

Mostly this a version of livelogging from the Hardfought server,
with some changes.

src/potion.c

@@ -2262,7 +2262,8 @@ dodip(void)
             short save_otyp = obj->otyp;
 
             /* KMH, conduct */
-            u.uconduct.polypiles++;
+            if (!u.uconduct.polypiles++)
+                livelog_printf(LL_CONDUCT, "polymorphed %s first item", uhis());
 
             obj = poly_obj(obj, STRANGE_OBJECT);