Add concurrency test 1013

Adds ta_concurrent and test case 1013 to test concurrent execution.

Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
Tested-by: Jerome Forissier <jerome.forissier@linaro.org> (HiKey)
Tested-by: Jens Wiklander <jens.wiklander@linaro.org> (qemu, FVP)
diff --git a/host/xtest/Makefile b/host/xtest/Makefile
index 1ea5a88..bcb89c7 100644
--- a/host/xtest/Makefile
+++ b/host/xtest/Makefile
@@ -71,6 +71,7 @@
 CFLAGS += -I../../ta/rpc_test/include
 CFLAGS += -I../../ta/sims/include
 CFLAGS += -I../../ta/storage/include
+CFLAGS += -I../../ta/concurrent/include
 ifdef CFG_GP_PACKAGE_PATH
 CFLAGS += -I../../ta/GP_TTA_Arithmetical
 CFLAGS += -I../../ta/GP_TTA_Crypto