Removed glew from building page, added hint that qt 5.6 is nnot yet supported

Documentation/DeveloperHelpSources/building.docu

@@ -9,9 +9,8 @@ OpenFlipper.
 
 \section reqlibs Required libraries
 <ul>
-<li> Qt >= 4.8.6  ( http://www.qt.io/download/ ) Use the OpenGL version for Qt >= 5.0</li>
+<li> 5.5 >= Qt >= 4.8.6  ( http://www.qt.io/download/ ) Use the OpenGL version for Qt >= 5.0</li>
 <li> GLUT         ( http://www.opengl.org/resources/libraries/glut/ )</li>
-<li> GLEW (>=1.6) ( http://glew.sourceforge.net )</li>
 </ul>
 
 \section optlibs Optional libraries ( Without these libraries some functionality might not be available)