Make SwSection::GetSectionName() return a reference to the name

Has a small but measureable impact on the time it takes to load a
specific pathological (huge) customer document. The load time drops
from 1min 46s to 1min 38s on my machine.

Reviewed-on: https://gerrit.libreoffice.org/46847Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>
Tested-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>
(cherry picked from commit 9675f307)

Change-Id: I93b603f369528187980d644a5364fa9bcf2f4615
Reviewed-on: https://gerrit.libreoffice.org/46904Reviewed-by: Tor Lillqvist <tml@collabora.com>
Tested-by: Tor Lillqvist <tml@collabora.com>

sw/inc/section.hxx

@@ -166,7 +166,7 @@ public:
 
     void SetSectionData(SwSectionData const& rData);
 
-    OUString GetSectionName() const         { return m_Data.GetSectionName(); }
+    const OUString& GetSectionName() const         { return m_Data.GetSectionName(); }
     void SetSectionName(OUString const& rName){ m_Data.SetSectionName(rName); }
     SectionType GetType() const             { return m_Data.GetType(); }
     void SetType(SectionType const eType)   { return m_Data.SetType(eType); }

sw/source/core/docnode/ndsect.cxx

@@ -1371,7 +1371,7 @@ OUString SwDoc::GetUniqueSectionName( const OUString* pChkStr ) const
         const SwSectionNode *const pSectNd = pFormat->GetSectionNode();
         if( pSectNd != nullptr )
         {
-            const OUString rNm = pSectNd->GetSection().GetSectionName();
+            const OUString& rNm = pSectNd->GetSection().GetSectionName();
             if (rNm.startsWith( aName ))
             {
                 // Calculate the Number and reset the Flag