fix assert on export of fdo77716-1.docx to odt

SwWriteTableCols becomes unsorted because rCol.nPos is < COLFUZZY

and it is unsigned so integer overflow on comparison. Just just move rhs
subtract to lhs add.

Change-Id: Ie037e8ba914a4c00e51d9dd1e0a0af9e1f4d353b

sw/source/filter/inc/wrtswtbl.hxx

@@ -204,7 +204,7 @@ inline bool SwWriteTableCol::operator<( const SwWriteTableCol& rCol ) const
 {
     // Da wir hier nur die Wahrheits-Grade 0 und 1 kennen, lassen wir lieber
     // auch nicht zu, dass x==y und x<y gleichzeitig gilt ;-)
-    return nPos < rCol.nPos - COLFUZZY;
+    return nPos + COLFUZZY < rCol.nPos;
 }
 
 struct SwWriteTableColLess {