internal/egl: call eglTerminate after context release

Without eglTerminate, using EGL will crash or report spurious errors after
creating and destroying enough contexts. The test program in #528
takes 5-10 window cycles before errors show up for me.

Fixes: https://todo.sr.ht/~eliasnaur/gio/528
Signed-off-by: Elias Naur <mail@eliasnaur.com>

internal/egl/egl.go

@@ -62,6 +62,7 @@ func (c *Context) Release() {
 		eglDestroyContext(c.disp, c.eglCtx.ctx)
 		c.eglCtx = nil
 	}
+	eglTerminate(c.disp)
 	c.disp = nilEGLDisplay
 }