libut is a bundling of uthash and its extra headers (utstring, etc,
and including utvector/utmm) into a libut.h header and libut.a library. 

It was copied from uthash itself (https://github.com/troydhanson/uthash).
It relies on uthash as a submodule, thus needs to be cloned recursively.

    git clone --recursive https://github.com/troydhanson/libut.git
