glretrace: GLX and WGL support for ES2/EGL traces.

I was able to glretrace Gears for Android on x86 Linux with
NVIDIA (non-DRI supporting) driver by enabling
GLX_CONTEXT_ES2_PROFILE_BIT_EXT for the
glXCreateContextAttribsARB path.

Unfortunately eglretrace via Mesa es2/egl doesn't seem
to be compatible the NVIDIA desktop driver.