Consistently use the #include "..." form for exactly those cases where the
included file is located next to the including file, see the mail thread
starting at
<https://lists.freedesktop.org/archives/libreoffice/2017-October/078601.html>
"C[++]: Normalizing include syntax ("" vs <>)".  (For UNO API include files,
see 189abcf0 "loplugin:includeform: UNO API
include files".)

(Some of the commits done earlier with messages containing "Change done in
preparation of loplugin:includeform" etc. were based on a somewhat different
earlier version of this plugin and would not be necessary with the current form.
But they are harmless and reverting them would probably cause more noise than
benefit, so just leave them in.)

Change-Id: I9fe9268ed84d31b5df71857a2e535972b11254ce
Reviewed-on: https://gerrit.libreoffice.org/43730Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>