top: improve/correct several memory fields in man page

top: improve/correct several memory fields in man page

Due to quirks in kernel memory management plus limited
information available from /proc/<pid>/status & statm,
some of the top resident memory fields were capable of
exceeding available physical memory. So this commit is
a bit of a band-aid until the kernel has been changed.

Such a change appears to be on the horizon in the form
of three new fields to be added to /proc/<pid>/status.
While not preventing 'resident' memory from apparently
exceeding physical memory, the new fields will help to
clarify any such contingency, if/when we exploit them.

Reference(s):
. original post by Samuel Thibault
https://gitlab.com/procps-ng/procps/issues/21
. informative memory analysis
https://techtalk.intersec.com/2013/07/memory-part-1-memory-types/
https://techtalk.intersec.com/2013/07/memory-part-2-understanding-process-memory/
. kernel changes to /proc/<pid>/status
commit 8cee852ec53fb530f10ccabf1596734209ae336b
commit eca56ff906bdd0239485e8b47154a6e73dd9a2f3

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