Partial XEP-0124 implementation to enable http-binding for clients.
Testing and debugging purpose only.
First XEP-0124 commit

	new file:   c2s/c2s_http.c
	modified:   c2s/Makefile.am
	modified:   c2s/c2s.c
	modified:   c2s/c2s.h
	modified:   c2s/main.c
	modified:   etc/c2s.xml.dist.in
	modified:   util/nad.c
	modified:   util/nad.h