Wrong valgrind version check

The version check in QBenchmarkValgrindUtils::haveValgrind() fails for Valgrind version like 3.10.5 because of a wrong regular expression:

QRegExp rx(QLatin1String("^valgrind-([0-9]).([0-9]).[0-9]"));

It should be:

QRegExp rx(QLatin1String("^valgrind-([0-9]+).([0-9]+).[0-9]"));