Utils: Introduce a not-so-abstract MacroExpander utility class

The current use of AbstractMacroExpander requires some boiler plate
code that can be avoided.

Change-Id: I753d872d824274d94d5105232a8fc05ac7bf0711
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>

src/libs/utils/stringutils.h

@@ -32,6 +32,8 @@
 
 #include "utils_global.h"
 
+#include <functional>
+
 QT_BEGIN_NAMESPACE
 class QStringList;
 QT_END_NAMESPACE
@@ -75,6 +77,19 @@ private:
     bool expandNestedMacros(const QString &str, int *pos, QString *ret);
 };
 
+class QTCREATOR_UTILS_EXPORT MacroExpander : public AbstractMacroExpander
+{
+public:
+    typedef std::function<bool(const QString &name, QString *ret)> Resolver;
+
+    explicit MacroExpander(const Resolver &resolver) : m_resolver(resolver) {}
+
+    bool resolveMacro(const QString &name, QString *ret) { return m_resolver(name, ret); }
+
+private:
+    Resolver m_resolver;
+};
+
 QTCREATOR_UTILS_EXPORT void expandMacros(QString *str, AbstractMacroExpander *mx);
 QTCREATOR_UTILS_EXPORT QString expandMacros(const QString &str, AbstractMacroExpander *mx);