Merge commit '8b9bcec' into dtls

* commit '8b9bcec':
  Stop assuming chars are signed
  Fix len miscalculation in buffer-based allocator
  Fix NULL dereference in buffer-based allocator
  Add test_suite_memory_buffer_alloc
  Add memory_buffer_alloc_self_test()
  Fix missing bound check
  Add test for ctr_drbg_update() input sanitizing
  Refactor for clearer correctness/security
  Stop assuming chars are signed

Conflicts:
	library/ssl_tls.c