Lint checking Octave

[Rik]

Task #8 on the release checklist is to run various lint checkers on the
Octave code base and fix any results.

Someone has kindly run a static analyzer on the Octave code base which has
produced many warnings that need to be looked at and either fixed or
dismissed.  I have created a page to track the status of this at
https://wiki.octave.org/PVS_static_analyzer_-_5.0_Release.  The original
bug report is at https://savannah.gnu.org/bugs/?55347.  If you have
changesets that fix one of the issues you should upload them to bug #55347
so that one of the Octave Maintainer's can apply them.

--Rik