Algorithms: Introduce helper Utils::equal

Takes a member (function) pointer and a value and returns a functor,
that takes a instance of the mfp's class and returns whether it's equal
to value. Sounds complicated, but is a common pattern that is easy to
understand.

Change-Id: Iaaeb90488d34ddfd6940dadd4c66705381198fee
Reviewed-by: Nikita Baryshnikov <nib952051@gmail.com>
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

src/plugins/projectexplorer/buildconfiguration.cpp

@@ -161,9 +161,7 @@ QList<Core::Id> BuildConfiguration::knownStepLists() const
 
 BuildStepList *BuildConfiguration::stepList(Core::Id id) const
 {
-    return Utils::findOrDefault(m_stepLists, [id](BuildStepList *list) {
-        return id == list->id();
-    });
+    return Utils::findOrDefault(m_stepLists, Utils::equal(&BuildStepList::id, id));
 }
 
 QVariantMap BuildConfiguration::toMap() const