util: use glib memory allocation functions

util: use glib memory allocation functions

Convert the VIR_ALLOC family of APIs with use of the g_malloc family of
APIs. Use of VIR_ALLOC related functions should be incrementally phased
out over time, allowing return value checks to be dropped. Use of
VIR_FREE should be replaced with auto-cleanup whenever possible.

We previously used the 'calloc-posix' gnulib module because mingw does
not set errno to ENOMEM on failure.

Reviewed-by: Ján Tomko <jtomko@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>