Bug 1202 - Add support of Adaptive Vsync via [GLX|WGL]_EXT_swap_control_tear

[GLX|WGL]_EXT_swap_control_tear extensions support
asynchronous buffer swaps, i.e. adaptive Vsync.

<https://www.opengl.org/wiki/SwapInterval_aka_vsync#Adaptive_Vsync>
<https://www.opengl.org/registry/specs/EXT/wgl_swap_control_tear.txt>
<https://www.opengl.org/registry/specs/EXT/glx_swap_control_tear.txt>

<http://keithp.com/blogs/async_flip/>

The extensions utilizes a negative interval value,
enabling late swaps to occur without synchronization to the video frame.

Hence '-1' has new semantics, previously it was the 'default value'
of 'untouched vsync interval'.

New default is:
  - 0 for unrealized context
  - 1 for realized context

+++

It requires [GLX|WGL]_EXT_swap_control,
hence we shall ensure to use use this extension
in the implementation of GLContext.setSwapInterval(..).

+++

Mesa3D seems to support GLX_SGI_swap_control only.

+++

Implemented on Windows and X11.

+++

On GNU/Linux using NVidia driver w/ my setup(*), sadly the query
  GLX.glXQueryDrawable(displayHandle, drawable.getHandle(), GLX.GLX_LATE_SWAPS_TEAR_EXT, val);
always returns zero here, indicating async vsync is not supported.

(Queried the attribute for every frame in windowed or fullscreen mode)

Fullscreen
(*)
  - Debian 8
  - Kernel 3.16
  - KDE/Kwin
  - GL Version     4.5 (Core profile, arb, compat[ES2, ES3, ES31], FBO, hardware) - 4.5.0 NVIDIA 355.06 [GL 4.5.0, vendor 355.6.0 (NVIDIA 355.06)]
  - GL_RENDERER    GeForce GTX 660/PCIe/SSE2
  - Samsung U28D590 (DFP-4): Internal DisplayPort

+++

1 files changed, 11 insertions, 2 deletions

diff --git a/src/jogl/classes/jogamp/opengl/macosx/cgl/MacOSXCGLContext.java b/src/jogl/classes/jogamp/opengl/macosx/cgl/MacOSXCGLContext.java
index d4fc0b005..2f88e7619 100644
--- a/src/jogl/classes/jogamp/opengl/macosx/cgl/MacOSXCGLContext.java
+++ b/src/jogl/classes/jogamp/opengl/macosx/cgl/MacOSXCGLContext.java
@@ -423,8 +423,17 @@ public class MacOSXCGLContext extends GLContextImpl
   }
 
   @Override
-  protected boolean setSwapIntervalImpl(final int interval) {
-    return impl.setSwapInterval(interval);
+  protected final Integer setSwapIntervalImpl(final int interval) {
+      final int useInterval;
+      if( 0 > interval ) {
+          useInterval = Math.abs(interval);
+      } else {
+          useInterval = interval;
+      }
+      if( impl.setSwapInterval(useInterval) ) {
+          return Integer.valueOf(useInterval);
+      }
+      return null;
   }
 
   @Override