egl/display: workaround gbm platforms without EGL 1.5 cilent

Some EGL drivers report the KHR extension with EGL 1.4, which doesn't
make any sense, however given that the constant for MESA and KHR is the
same, we can check for KHR in MESA branch, but still use the Ext
functions.

Fixes #1708.

CHANGELOG.md

@@ -10,6 +10,7 @@
 - Added `NotCurrentContext::make_current_surfaceless(self)` and
   `PossiblyCurrentContext::make_current_surfaceless(&self)` in the `Wgl`
   implementation to allow the use of surfaceless contexts with WGL.
+- Added workaround for EGL drivers reporting `EGL_KHR_platform_gbm` without EGL 1.5 client.
 
 
 # Version 0.32.1

glutin/src/api/egl/display.rs

@@ -362,7 +362,16 @@ impl Display {
                     handle.connection.map_or(egl::DEFAULT_DISPLAY as *mut _, |c| c.as_ptr()),
                 )
             },
-            RawDisplayHandle::Gbm(handle) if extensions.contains("EGL_MESA_platform_gbm") => {
+            RawDisplayHandle::Gbm(handle)
+                // NOTE: Some drivers report that they support the KHR GBM extension without EGL
+                // 1.5 client, so work around that here by checking the KHR GBM extension as well.
+                // The MESA and KHR extensions have the same constant values, thus it'll work
+                // regardless.
+                //
+                // See https://github.com/rust-windowing/glutin/issues/1708.
+                if extensions.contains("EGL_MESA_platform_gbm")
+                    || extensions.contains("EGL_KHR_platform_gbm") =>
+            {
                 (egl::PLATFORM_GBM_MESA, handle.gbm_device.as_ptr())
             },
             RawDisplayHandle::Drm(_) => {