Initial commit

It's still a fortran code, but at least it's configured by cmake.
You need a global installation of LHAPDFs, and Cuba to make. Otherwise
you need to provide the paths to the local version of these libs
yourself in src/CMakeLists.txt.

To compile:
cd build
cmake ../src/
make

If you want to compile somewhere else, you need to supply (in the
runcard) the path to data/HdecayGrid.dat *relative* to the directory of
the executable ihixs. If you build at 'build' the path in the runcard
(default set to ../data/HdecayGrid.dat) works.