stcp: ed25519 pubkey exchange in handshake, fix instance destroy segfault, fix chat_tcp_test

- u_async.c: process immediate_queue BEFORE epoll_wait in uasync_poll
- stcp_link.c: defensive NULL etcp_conn/etcp_link in stcp_link_close
- utun_instance.c: move stcp_server_list_destroy_all to Phase J (before ETCP),
  add deferred drain in both Phase J and L
- stcp.h/c: STCP_HS_ENC_CLIENT 6→38, STCP_HS_ENC_SERVER 7→39,
  exchange ed25519_pubkey in both handshake directions
- etcp_connections.c: copy peer_ed25519 from STCP to ETCP_CONN in
  etcp_link_enter_ready_tcp; guard link->etcp in tcp_link_close_cb
- chat_sync.c: fix lk->conn NULL dereference for TCP links
- test_stcp.c: update stcp_server_create/stcp_client_connect callsites
- tools/chat_tcp_test: change transport udp→tcp

tinycrypt/config.mk

@@ -0,0 +1,35 @@
+################################################################################
+#
+#      Copyright (C) 2017 by Intel Corporation, All Rights Reserved.
+#
+#            Global configuration Makefile. Included everywhere.
+#
+################################################################################
+
+# EDIT HERE:
+CC:=gcc
+CFLAGS:=-Os -std=c99 -Wall -Wextra -D_ISOC99_SOURCE -MMD -I../lib/include/ -I../lib/source/ -I../tests/include/
+vpath %.c ../lib/source/
+ENABLE_TESTS=true
+
+# override MinGW built-in recipe
+%.o: %.c
+	$(COMPILE.c) $(OUTPUT_OPTION) $<
+
+ifeq ($(OS),Windows_NT)
+DOTEXE:=.exe
+endif
+
+# DO NOT EDIT AFTER THIS POINT:
+ifeq ($(ENABLE_TESTS), true)
+CFLAGS += -DENABLE_TESTS
+else
+CFLAGS += -DDISABLE_TESTS
+endif
+
+export CC
+export CFLAGS
+export VPATH
+export ENABLE_TESTS
+
+################################################################################