Fixes#74
Provides new functionality to build Client Only or Server Only code.
Provides new functionality to include TCP (and hence TLS) support.
Removes the requirement for -Wno-warning
if COAP_CONSTRAINED_STACK is defined (is for esp-idf), the mutexes set up
to protect the critical sections were not working as expected and were just
dummy entries.
Use the pthread_ version of the mutex instead by defining HAVE_PTHREAD_H
and HAVE_PTHREAD_MUTEX_LOCK.
Harshit Malpani