test: provide unit test for memory functions

Memory functions may have architecture specific implementations. These
should be tested.

Provide unit tests for memset(), memcpy(), memmove().

Provide a 'ut lib' sub-command to execute the tests.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/test/lib/Makefile b/test/lib/Makefile
index 5a636aa..308c617 100644
--- a/test/lib/Makefile
+++ b/test/lib/Makefile
@@ -2,5 +2,7 @@
 #
 # (C) Copyright 2018
 # Mario Six, Guntermann & Drunck GmbH, mario.six@gdsys.cc
+obj-y += cmd_ut_lib.o
 obj-y += hexdump.o
 obj-y += lmb.o
+obj-y += string.o