Implement #include<sys/user.h> and #include<sys/procfs.h>

Up until this patch it is possible to build gnu based (glibc) relibc cross platform This patch is for building stage2 binutils. The firs issue I faced is missing procfs and this patch should take care of that.

This patch re-implements sys/user.h file that works for both x86_64 as well as aarch64. This include file is used by sys/procfs.h which is needed dependency for binutils. There is bug in this patch in aarch64 implementation which is the lack of f128 implementation in rust, thus we can't create cbinding for long double.