obj->oextra->{omid,olong}

Change obj->oextra->omid from a usually-Null pointer field in
oextra to a simple 'unsigned' that doesn't need any allocation
beyond obj->oextra itself.  Value 0 means that it is not in use;
it is used to hold a monst.m_id and those are always non-zero.

Delete unused obj->oextra->olong.  'olong' used to be the last
field in struct obj, put there to force alignment of anything
which followed it back when obj structures were over-allocated to
append extra information.  It had a comment about being used for
temporary gold but whatever that was, temporary gold was gone long
before obj->oextra got introduced.

Bump EDITLEVEL since this invalidates existing 3.7 save files.

Remove a bunch of tabs from obj.h and save.c.

src/zap.c

@@ -873,8 +873,7 @@ boolean by_hero;
         struct monst *ghost;
         struct obj *otmp;
 
-        (void) memcpy((genericptr_t) &m_id, (genericptr_t) OMID(corpse),
-                      sizeof m_id);
+        m_id = OMID(corpse);
         ghost = find_mid(m_id, FM_FMON);
         if (ghost && ghost->data == &mons[PM_GHOST]) {
             if (canseemon(ghost))