Do not query the row count repeatedly.

The compiler is not smart enough to hoist this call out
of the loop. But we can expect that the row count will not
change during a call to filterAcceptsRow.

src/krecursivefilterproxymodel.cpp

@@ -301,7 +301,7 @@ bool KRecursiveFilterProxyModel::filterAcceptsRow(int sourceRow, const QModelInd
     Q_ASSERT(source_index.isValid());
     bool accepted = false;
 
-    for (int row = 0; row < sourceModel()->rowCount(source_index); ++row) {
+    for (int row = 0, rows = sourceModel()->rowCount(source_index); row < rows; ++row) {
         if (filterAcceptsRow(row, source_index)) {
             accepted = true;
             break;