registry: fix compilation with --disable-registry
registry: fix compilation with --disable-registry

__registry_reuse_plugin_scanner is only defined when
GST_DISABLE_REGISTRY is not defined.

gstregistry.c: In function 'gst_registry_scan_plugin_file':
gstregistry.c:1131:8: error: '__registry_reuse_plugin_scanner' undeclared (first use in this function)

https://bugzilla.gnome.org/show_bug.cgi?id=667284

Distrotech/gstreamer,Distrotech/gstreamer,Distrotech/gstreamer,Distrotech/gstreamer,Distrotech/gstreamer