Fix fence-post error in my re-write of SplitProcLine().

I was leaving ep pointing at the last character of the space-delimited
field, not at the character after it.  How did that even work on the
systems where it did ?
Clean-up and documentation in processes_select.c

Corrected a Log() message that thought it only related to elapsed
time; it could also relate to other times.  Use isspace() rather
than only comparison to ' ' in case there are tabs.

Made some variables more local, made some comments clearer, added some
comments.  Petty consistency in typography of isspace() calls.
Merge pull request #1905 from ediosyncratic/ps-parse-fix

Fix an off-by-one error in my recent rework of SplitProcLine()