[Libvir] [PATCH] Readd buffer errors & some cleanups

This readds some error checking of the returns from virBuffer* functions, removes need for is_blank (a _GNU_SOURCE extension), and a couple of other very minor cleanups. 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