tools/libxc: C implementation of stream format

tools/libxc: C implementation of stream format

Provide the C structures matching the binary (wire) format of the new
stream format.  All header/record fields are naturally aligned and
explicit padding fields are used to ensure the correct layout (i.e.,
there is no need for any non-standard structure packing pragma or
attribute).

Provide some helper functions for converting types to string for
diagnostic purposes.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Ian Campbell <Ian.Campbell@citrix.com>