miniupnpd: detect port in use / already forwarded

Patch submitted by David Kerr
Merge branch 'master' into portinuse

Conflicts:
	README
Merge branch 'master' into portinuse
APIVERSION = 10
miniupnpc/Makefile: fix clean target
miniupnpc.c: translate comment from French to English :)
miniupnpd/minissdp.c: check return value of AddMulticastMembershipIPv6()
miniupnpd.c: comments in parselanaddr()
miniupnpd: removed unused code

ScanNATPMPforExpiration() CleanExpiredNATPMP() are not used anymore
miniupnpd: define min/max_lifetime only when needed
miniupnpd: various PCP fixes
miniupnpd:  PCP Add support for ANNOUNCE requests
minixml.c: now handle XML comments
minissdpd/listifaces: fix. now compatible with linux and BSD
minissdpd.c: improve comments and logging
minissdpd.c: silently ignore EAGAIN, EWOULDBLOCK, EINTR of recv calls
minissdpd.c: Discover devices on the network at startup
miniupnpc/connecthostport.c: handle EINPROGRESS after connect()
removed unused stuff
upnpc.c: 2013 -> 2014