enable more opengl chipsets

[Antoine Martin]

Follow up from ticket:1358#comment:5, enhance the GL check code to create a temporary window with textures and go through one fake paint call to verify that the opengl driver is usable.

[Antoine Martin]

Done in r15007:

• greylisted chipsets are now enabled, you will see a warning similar to this one:

  Warning: vendor 'NVIDIA Corporation' is greylisted,
   you may want to turn off OpenGL if you encounter bugs
  

• we test rendering using a hidden temporary opengl window
• the errors from #1358 are no longer ignored, and should cause the rendering test to fail with a message similar to this one:

  OpenGL test rendering failed:
   OpenGL RGBX paint error: GLError(
   	err = 1281,
   	description = 'invalid value',
   	baseOperation = glClear,
   	cArguments = (116384,)
   )
  

And opengl should be disabled on those broken chipsets.

[Antoine Martin]

Intel driver woes continue: ticket:1469#comment:14.

[Antoine Martin]

Works as well as can be expected, next step will be opengl in python3: #1569

[migration script]

this ticket has been moved to: ​https://github.com/Xpra-org/xpra/issues/1367