[Libvir] 21/22 Disable exec in util.c

It's not likely that the external programs will actually exist on MinGW anyway, so execing them isn't very useful. This also removes the virFileLinkPointsTo function, which I think is only used by libvirtd anyway. Rich. -- Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/ Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 03798903