Implement setting wxGLCanvas attributes in wxQt

Simply remove the premature "return true" which was somehow added back
in df13791078 (Merge wxQT branch into the trunk., 2014-08-24) and add
WX_GL_MAJOR_VERSION support.

src/qt/glcanvas.cpp

@@ -425,7 +425,6 @@ bool wxGLCanvas::ConvertWXAttrsToQtGL(const int *wxattrs, QGLFormat &format)
 {
     if (!wxattrs)
         return true;
-    return true;
 
     // set default parameters to false
     format.setDoubleBuffer(false);
@@ -513,6 +512,10 @@ bool wxGLCanvas::ConvertWXAttrsToQtGL(const int *wxattrs, QGLFormat &format)
                 // can we somehow indicate if it's not supported?
                 break;
 
+            case WX_GL_MAJOR_VERSION:
+                 format.setVersion ( v,0 );
+                 break;
+
             default:
                 wxLogDebug(wxT("Unsupported OpenGL attribute %d"),
                            wxattrs[arg]);