cppcheck: use prefix variant

unoxml/source/dom/saxbuilder.cxx

@@ -263,10 +263,8 @@ namespace DOM
             attr_qname = a->first;
             attr_value = a->second;
             idx = attr_qname.indexOf(':');
-            if(idx != -1)
-            {
+            if (idx != -1)
                 aPrefix = attr_qname.copy(0, idx);
-            }
             else
                 aPrefix = OUString();
 
@@ -275,11 +273,13 @@ namespace DOM
             {
                 // set attribute with namespace
                 aElement->setAttributeNS(result->second, attr_qname, attr_value);
-            } else {
+            }
+            else
+            {
                 // set attribute without namespace
                 aElement->setAttribute(attr_qname, attr_value);
-           }
-            a++;
+            }
+            ++a;
         }
         m_aNSStack.push(aNSMap);
     }

unoxml/source/xpath/xpathapi.cxx

@@ -134,7 +134,7 @@ namespace XPath
             p = (xmlChar*)oprefix.getStr();
             u = (xmlChar*)ouri.getStr();
             xmlXPathRegisterNs(ctx, p, u);
-            i++;
+            ++i;
         }
     }
 
@@ -185,7 +185,7 @@ namespace XPath
                     reinterpret_cast<void*>(
                         sal::static_int_cast<sal_IntPtr>(aHandle.variableData)));
             }
-            i++;
+            ++i;
         }
     }