misc: tweaks (mostly cosmetic) to several source files

. a more appropriate error return code was substituted
. a safer form of comparison is utilized in two places
. a STAT_VAL macro replaced by more proper MEMINFO_VAL
. several of the silly 'xerrx' formats had been missed
. a few whitespace changes have also been incorporated

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

proc/slabinfo.c

@@ -994,7 +994,7 @@ PROCPS_EXPORT struct slabinfo_stack **procps_slabinfo_sort (
         if (p->item == sortitem)
             break;
         ++offset;
-        if (p->item == SLABINFO_logical_end)
+        if (p->item >= SLABINFO_logical_end)
             return NULL;
         ++p;
     }