intx for Unikraft

This is the port of intx for Unikraft as external library.

Build

intx depends on the following libraries, that need to be added to Makefile in this order:

• CXX standard library, e.g. libunwind, compiler-rt, libcxxabi, libcxx
• libc, e.g. newlib
• googletest when building the unittests

Please refer to the README.md as well as the documentation in the doc/ subdirectory of the main unikraft repository.