[libextractor] Wrong check for ole2

[Heikki Lindholm]

This seems wrong to me:
in src/main/extractor.c
#if HAVE_GLIB
#define OLESO "libextractor_ole2:"
#else
...
It's quite likely to have glib without having libgsf, in which case ole2 
won't be built, it seems. There should be a HAVE_LIBGST or something 
like that, instead.

-- Heikki Lindholm