[cpp.include] tells that includes in <> are searched in implementation-defined
places; includes in "" are searched in other implementation-defined places,
and is unsuccessful, then as if they were in <>.

MS VisualStudio IDE uses paths configured for the project for includes
in <>, and starts with current file paths for includes in "". So, using
<> for includes in current source file's directory missing from configured
project paths makes IDE show unsuccessful includes and unknown identifiers.

This fixes includes in writerfilter source directory.

Change-Id: I0bc1147aa68c305afd0c119418f07b655783a466
Reviewed-on: https://gerrit.libreoffice.org/43138Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>