[Qt] LCLQt vs LCLQt5

[Heiko Tietze]

With Qt5 we got a new switch. However, some if not all source files still use LCLQt. For example in OpenGLContext 

{$IFDEF LCLQT}
  {$DEFINE UseQTGLX}
  ...

and in GLQTContext

  // Bindings
  {$ifdef LCLQT} qt4, {$endif}

The first can be solved with {$IF Defined(LCLQT) or Defined(LCLQT5)} the second works per {$ifdef LCLQT} qt4, {$else} qt5, {$endif}¹. But I wonder if we better keep LCLQt for all Qt variants and introduce a 'legacy' LCLQt4 switch additional to the new LCLQt5.

Great work anyway, enabling Qt5 was a piece of cake compared to the handling of Qt in the past.
Heiko

¹ Despite the fact that OpenGL neither works with Qt4 nor Qt5.