On some systems we must the struct in_pktinfo and in6_pktinfo defining
by ourself. But on POSIX systems the definition is made by the header
netinet/in.h, so check if there is a flag HAVE_NETINET_IN_H been set and
skip the self made definition.
In preparation for changing the make buildsystem to a fully autotools
controlled system moving the core libcoap source files to a better logical
place.
All the library related header files moving to include/coap/ to get
all the public and local header files in a separate place. Also moving
the C source files of the libcoap library to the folder src/.
Olaf Bergmann