library: eliminate one potential source of human error

There's a huge toe-stubber awaiting future maintenance
as reflected in that commit below which deals with the
addition of new enumerators to the Item_table. Namely,
whenever the table is grown, one must remember to also
change that existing 'logical_end' enumerator's value.

Well, not anymore! Since that MAXTABLE macro was added
to the procps-private.h header we can now also exploit
it so a 'logical_end' automatically tracks table size.

This change also renders some code associated with the
ITEMTABLE_DEBUG #define unnecessary. So it's gone too.

Reference(s):
. 08/2016, add new enumerators
commit 09e1886c9e
. 08/2020, added MAXTABLE macro
commit c865b06c30
. 08/2020, introduced ITEMTABLE_DEBUG
commit 92d0297e1e

Signed-off-by: Jim Warner <james.warner@comcast.net>

proc/slabinfo.c

@@ -311,7 +311,7 @@ static struct {
 
     /* please note,
      * this enum MUST be 1 greater than the highest value of any enum */
-enum slabinfo_item SLABINFO_logical_end = SLABS_DELTA_SIZE_TOTAL + 1;
+enum slabinfo_item SLABINFO_logical_end = MAXTABLE(Item_table);
 
 #undef setNAME
 #undef srtNAME
@@ -753,11 +753,6 @@ PROCPS_EXPORT int procps_slabinfo_new (
             failed = 1;
         }
     }
-    if (i != SLABINFO_logical_end) {
-        fprintf(stderr, "%s: SLABINFO_logical_end is %d, expected %d\n"
-            , __FILE__, SLABINFO_logical_end, i);
-        failed = 1;
-    }
     if (failed) _Exit(EXIT_FAILURE);
 #endif