Annotate intentional case fallthrough, or add breaks.

Annotate intentional case fallthrough, or add breaks.

Fix suspicious (*) switch cases found by Coverity by
annotating with either "/* FALLTHROUGH */" or adding a break;

The FALLTHROUGH was much more common, but the break turned
out to be the right choice in three spots.  All changes tested
to work.

(*) suspicious = case1 + code + case2, and neither flow control
(like break) nor fallthrough annotation between code and case2.

Fix for Coverity perl5 CIDs 28977..28989, 45353.