As unit tests with IPv6 addresses keep failing on docker-based
travis CI, this changes reverts to IPv4 usage in following files:
test_wellknown.c
test_sendqueue.c
Sendqueue nodes and send operations now require a session object.
This modification calls coap_new_client_session() on a global
coap_context_t object to create a fake session on the loopback
interface.
The testdriver was linked against the statically generated library of
libcoap. By this the testdriver will *always* find any symbols, no
matter if it is a private or public symbol.
Due this the testing behavior isn't the same as a user would use the
shared library and can get a potentially pitfall even if the testdriver
was successful.
Due previous changes to the public header the testdriver source needs
now the local header coap_config.h to find all needed functions so there
are small changes needed to the source files.
Olaf Bergmann