khronos: backport typedef for EGL_EXT_image_dma_buf_import

The `gstreamer1.0-plugins-base` package version `1.14` uses `EGL_EXT_image_dma_buf_import`, which
expects the `EGLuint64KHR` typedef that is present in recent versions of Khronos.
However, the older version included in userland does not provide it.

This patch backports the missing typedef from recent Khronos into userland.
See: <https://www.khronos.org/registry/EGL/api/EGL/eglext.h>

Submitted to userland in <raspberrypi#467>

Upstream-Status: Submitted

interface/khronos/include/EGL/eglext.h

@@ -190,6 +190,10 @@ typedef EGLBoolean (EGLAPIENTRYP PFNEGLSIGNALSYNCKHRPROC) (EGLDisplay dpy, EGLSy
 typedef EGLBoolean (EGLAPIENTRYP PFNEGLGETSYNCATTRIBKHRPROC) (EGLDisplay dpy, EGLSyncKHR sync, EGLint attribute, EGLint *value);
 #endif
 
+#ifndef EGL_KHR_uint64_typedef
+#define EGL_KHR_uint64_typedef 1
+typedef khronos_uint64_t EGLuint64KHR;
+#endif /* EGL_KHR_uint64_typedef */
 
 #ifndef EGL_WL_bind_wayland_display
 #define EGL_WL_bind_wayland_display 1