Update Qt requirement.

Change-Id: I8d3eb57a3cb41c4bfd01defc3f5c512a46a7a428
Reviewed-on: http://codereview.qt.nokia.com/1652


Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Daniel Molkentin <daniel.molkentin@nokia.com>

qtcreator.pro

+include(qtcreator.pri)
+
 #version check qt
-contains(QT_VERSION, ^4\\.[0-6]\\..*) {
+!minQtVersion(4, 7, 4) {
     message("Cannot build Qt Creator with Qt version $${QT_VERSION}.")
-    error("Use at least Qt 4.7.")
+    error("Use at least Qt 4.7.4.")
 }
 
-include(qtcreator.pri)
 include(doc/doc.pri)
 
 TEMPLATE  = subdirs