top: avoid yet more overhead of accessing /proc/status

top: avoid yet more overhead of accessing /proc/status

After discovering those terrible costs associated with
/proc/status vs. /proc/stat, our library changed so as
to favor the latter if a field could be met by either.

Well, low-and-behold, this top program had chosen some
item enumerators that needlessly caused 'status' to be
accessed when 'statm' could be used instead. And while
top's needs require conversion from pages to KiB, that
is still far less costly than that damn 'status' file.

[ this was found when comparing newlib top against a ]
[ 3.2.8 ancient top since the current master top was ]
[ suffering from the exact same 'status' deficiency. ]

[ and, no way was top-3.2.8 going to beat newlib top ]
[ by 50% - we'll allow only a 1-10% occasional loss! ]

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