g-i: silence 'nested extern' compiler warnings when building scanner binary

g-i: silence 'nested extern' compiler warnings when building scanner binary

We need a nested extern in our init section for the scanner binary
so we can call gst_init to make sure GStreamer types are initialised
(they are not all lazy init via get_type functions, but some are in
exported variables). There doesn't seem to be any other mechanism to
achieve this, so just remove that warning, it's not important at all.