Add tinycrypt 0.2.8

Signed-off-by: Fabio Utzig <utzig@apache.org>
diff --git a/ext/tinycrypt/config.mk b/ext/tinycrypt/config.mk
index 9642066..a5b9fb7 100644
--- a/ext/tinycrypt/config.mk
+++ b/ext/tinycrypt/config.mk
@@ -1,11 +1,12 @@
 ################################################################################
 #
-#      Copyright (C) 2015 by Intel Corporation, All Rights Reserved.
+#      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/
@@ -19,11 +20,16 @@
 DOTEXE:=.exe
 endif
 
-# DO NOT EDIT THIS:
+# 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
+
 ################################################################################