Updated the signatures library to version 1.1 with one new method and corresponding test case

Change-Id: I2ab9d2783d1f5e6a6d680a2b532142bd4248b07a
Signed-off-by: John May <john.wilkinsonmay@gmail.com>
Signed-off-by: Egon Willighagen <egonw@users.sourceforge.net>