Don't create temporary substrings

Avoid temporary string allocations. They are only used to convert to
something else.
QString::xxxRef() returns a QStringRef. QStringRef avoids the memory
allocation and reference counting overhead of a standard QString by simply
referencing a part of the original string.

src/base/rss/rss_autodownloadrule.cpp

@@ -302,7 +302,7 @@ bool AutoDownloadRule::matches(const QString &articleTitle) const
                 QRegularExpression reg(cachedRegex(partialPattern1));
 
                 if (ep.endsWith('-')) { // Infinite range
-                    int epOurs = ep.left(ep.size() - 1).toInt();
+                    int epOurs = ep.leftRef(ep.size() - 1).toInt();
 
                     // Extract partial match from article and compare as digits
                     matcher = reg.match(articleTitle);