Use optimized string concatenation

Change-Id: If9d9af8255639e4d7e5c2e8020c1b3675498980f
Reviewed-on: https://gerrit.libreoffice.org/67657
Tested-by: Jenkins
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>

sc/source/ui/docshell/dbdocimp.cxx

@@ -343,9 +343,9 @@ bool ScDBDocFunc::DoImport( SCTAB nTab, const ScImportParam& rParam,
                             if (!(nInserted & 15))
                             {
                                 OUString aPict = ScResId( STR_PROGRESS_IMPORT );
-                                OUString aText = aPict.getToken(0,'#');
-                                aText += OUString::number( nInserted );
-                                aText += aPict.getToken(1,'#');
+                                OUString aText = aPict.getToken(0, '#')
+                                    + OUString::number( nInserted )
+                                    + aPict.getToken(1, '#');
 
                                 aProgress.SetStateText( 0, aText );
                             }