slirp: set G_LOG_DOMAIN

We are moving to g_log() facilities to log errors and probably debug
messages too. Let's have the "Slirp" prefix on messages slirp produces.
Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: NSamuel Thibault <samuel.thibault@ens-lyon.org>

slirp/Makefile.objs

@@ -28,3 +28,5 @@ slirp.mo-objs = \
 	udp.o \
 	udp6.o \
 	$(NULL)
+
+slirp.mo-cflags = -DG_LOG_DOMAIN=\"Slirp\"