Remove Qt version checks.

Qt 5.3 is the minimum requirement these days. Remove all fallback code
from sources and project files.

Change-Id: If6188a471197acadda4d6baee71804ba1a8026c6
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/libs/utils/algorithm.h

@@ -30,21 +30,11 @@
 #ifndef ALGORITHM_H
 #define ALGORITHM_H
 
+#include <qcompilerdetection.h> // for Q_REQUIRED_RESULT
+
 #include <algorithm>
 #include <functional>
 
-#if QT_VERSION < 0x050000
-    #ifndef Q_REQUIRED_RESULT
-    # if defined(Q_CC_GNU)
-    #   define Q_REQUIRED_RESULT __attribute__ ((warn_unused_result))
-    # else
-    #   define Q_REQUIRED_RESULT
-    # endif
-    #endif
-#else
-    #include <qcompilerdetection.h> // for Q_REQUIRED_RESULT
-#endif
-
 namespace Utils
 {
 //////////////////