top: minor refactor in preparation for other filtering

top: minor refactor in preparation for other filtering

While it's only documented (so far) in commit text and
an occasional email I've tried to maintain some coding
standards primarily for reference/navigation purposes.
They also served, I felt, as useful mental challenges.

Someday I will get around to formerly documenting them
but in the meantime here are the ones for this commit:

. functions are grouped into logical (i hope) sections
. functions & sections are ordered to avoid prototypes
. function names are alphabetical within every section

Thus, given those constraints/objectives, and in order
to prepare for an upcoming Other_Filter feature, a few
things had to be renamed and rearranged. Plus a couple
of other (unrelated) tweaks were made for consistency.

(everything is perfectly justified plus right margins)
(are completely filled, but of course it must be luck)

Reference(s):
commit 270e8e7eeb66b47569940f537cdad4ab46cd36be
http://www.freelists.org/post/procps/PATCH-12-top-restore-terminal-state-on-exit,4

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