related tdf#76683 writerfilter: hanging implemented as Signed

despite the documentation that states it must be a positive value,
the actual implmentation honors a negative number (as opposed to
treating it as a zero, or an absolute).

Change-Id: Ie38369ecdf5353b73572dd3533c2efe41adda290
Reviewed-on: https://gerrit.libreoffice.org/59401
Tested-by: Jenkins
Reviewed-by: Justin Luth <justin_luth@sil.org>

sw/qa/extras/ooxmlexport/ooxmlexport11.cxx

@@ -674,6 +674,7 @@ DECLARE_OOXMLEXPORT_TEST(testTdf118521_marginsLR, "tdf118521_marginsLR.docx")
     nMargin = getProperty<sal_Int32>(xMyStyle, "ParaRightMargin");
     CPPUNIT_ASSERT_EQUAL(sal_Int32(1900), nMargin);
     CPPUNIT_ASSERT_EQUAL(nMargin, getProperty<sal_Int32>(getParagraph(2), "ParaRightMargin"));
+    CPPUNIT_ASSERT_EQUAL(sal_Int32(882), getProperty<sal_Int32>(getParagraph(2), "ParaFirstLineIndent"));
 }
 
 DECLARE_OOXMLIMPORT_TEST(testTdf104797, "tdf104797.docx")

writerfilter/source/ooxml/model.xml

@@ -11784,7 +11784,7 @@
           <ref name="ST_DecimalNumber"/>
         </attribute>
         <attribute name="hanging">
-          <ref name="ST_TwipsMeasure"/>
+          <ref name="ST_TwipsMeasure_asSigned"/>
         </attribute>
         <attribute name="hangingChars">
           <ref name="ST_DecimalNumber"/>