gupnp-tools: fix when using latest gupnp-av

Include gupnp.h ourselves, gupnp-av.h doesn't drag it in anymore

Backported from: e9ec9634207e4c2eea6d268ee29b57e687c1f178
The patch retrieved from the official gnome URL
(https://git.gnome.org/browse/gupnp-tools/patch/?id=e9ec9634207e4c2eea6d268ee29b57e687c1f178)
can not be applied through GUPNP_TOOLS_PATCH as it does not end with the
'.patch*' pattern

Fixes:
  - http://autobuild.buildroot.org/results/329851daa060f23c55f996c1b0f323d41f85ccb2



Signed-off-by: Fabrice Fontaine <fabrice.fontaine@orange.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>