Clean up code so that UPnP implementation does not need to include all
the HTTP functionality. In addition, make it easier to share HTTP server
functionality with other components in the future.
This is the first step in adding support for using wpa_supplicant as a
WPS External Registrar to manage APs over UPnP. Only the device
discovery part is implemented in this commit.
This adds mostly feature complete external Registrar support with the
main missing part being proper support for multiple external Registrars
working at the same time and processing of concurrent registrations when
using an external Registrar.
This code is based on Sony/Saice implementation
(https://www.saice-wpsnfc.bz/) and the changes made by Ted Merrill
(Atheros) to make it more suitable for hostapd design and embedded
systems. Some of the UPnP code is based on Intel's libupnp. Copyrights
and licensing are explained in src/wps/wps_upnp.c in more detail.
