Export `gst_plugin_NAME_register()` and `gst_plugin_NAME_get_desc()` functions if targetting GStreamer >= 1.14
The following discussion from gst-plugin-rs!42 should be addressed:
With GStreamer >= 1.14 we should optionally just create a
GST_PLUGIN_DEFINEdoes. That makes everything easier for us as we can run actual code instead of having to statically create a C struct here.
It would also allow using actual strings instead of NUL-terminated byte arrays for the plugin metadata.