vo_opengl: angle: call eglTerminate()

I hope that this does what we expect it does: destroy the EGLDisplay
specific to our HDC. (Some implementations will terminate all EGL
contexts in the whole process.)

eglReleaseThread() merely calls eglMakeCurrent(0, 0, 0, 0), which is
not enough.

This commit also fixes the problem fixed with the previous commit,
but I think both changes are needed to make our API usage clean.

video/out/opengl/context_angle.c

@@ -39,6 +39,8 @@ static void angle_uninit(MPGLContext *ctx)
         eglDestroyContext(p->egl_display, p->egl_context);
     }
     p->egl_context = EGL_NO_CONTEXT;
+    if (p->egl_display)
+        eglTerminate(p->egl_display);
     vo_w32_uninit(ctx->vo);
 }