Made all manufacturer related information configurable:
- manufacturer_name, default is "`uname -s`"
- manufacturer_url, default is URL of OS verndor
- model_name, default is "`uname -s` router"
- model_description, default is "`uname -s` router"
- model_url, default is URL of OS verndor
some libc implementations don't define struct ip_mreqn
define it here if CFLAG passed with -DNEED_STRUCT_IP_MREQN

I found this issue cross compiling for ARM using eclibc in the
https://www.yoctoproject.org/  build system.
Merge pull request #45 from karlhiramoto/master

fix cross-compile:   some libc implementations don't define struct ip_mreqn
miniupnpc: define MAXHOSTNAMELEN if not already done
miniwget.c: fixed potential buffer overrun
miniupnpc.c: UPNP_GetValidIGD() now checks for ExternalIpAddress
testminiwget.sh: fix comment (it now works with dash)
upnpcommands.c: fixes potential null dereference. Fix #046
upnpc.c: --help and -h arguments

fixes #037
Merge remote-tracking branch 'upstream/master'
miniupnpd: Make all manufacturer info configurable
testupnpdescgen.c: minor fix on getifaddr()
miniupnpc.c: MX cannot be 0
typo fix
update .gitignore
update Changelog.txt :)
Makefile: add pcpserver.o
getifaddr: more portable code (works with old OpenBSD)
remove C++ style comments
pcpserver.c: small code simplification