new container flags

[Attention: This patch increments EDITLEVEL in patchlevel.h, rendering all
 previous save and bones files obsolete.]

Here's the first cut at the two recommended flags lknown and cknown.
I've attempted to stay close to Pat's recommendations:
   "Containers ought to have two new flags:  lknown for lock status known,
    and cknown for contents known (ie, `secret').  Formatted box and chest
    descriptions should include locked/unlocked/broken when that is known
    and empty/nonempty (or something like "holds N items") when contents
    are known. The contents indicator would also apply to nonlockable
    containers."

I probably overlooked a place where a flag should be adjusted, but this
should give us a good starting point.

I wasn't sure what to do with the case of the auditory feedback for
magical locking "Click" and "Clunk". The question that came to my mind
was: Should those reveal the locked or unlocked status of a box?
I suppose if you knew the type of wand you were zapping or the spell
you were casting, you could argue that they should.

In the end, I opted for setting lknown right off the zap/cast effect
for anyone playing a Wizard role, and not setting it for anyone else,
thus advancing class differentiation a little bit too.

I haven't checked the cknown results under all flags.menu_style options
at this point, only MENU_FULL.

src/mkobj.c

@@ -377,6 +377,8 @@ boolean artif;
 		otmp->dknown = 0;
 	if (!objects[otmp->otyp].oc_uses_known)
 		otmp->known = 1;
+	otmp->lknown = 0;
+	otmp->cknown = 0;
 #ifdef INVISIBLE_OBJECTS
 	otmp->oinvis = !rn2(1250);
 #endif