This code has been downloaded from 
https://github.com/DrTimothyAldenDavis/SuiteSparse
Available under BSD 3-clause license.

Changes:
- The name of the custom types and of some #define has been changed, to avoid conflicts.
- Any function that is not needed to use amd_order has been removed.
- The code is compiled using a single integer type, controlled by HIGHSINT64.