Provide backwards binary compatibility for the Hurd.
* hurd/geteuids.c [PIC && DO_VERSIONING]: Make __getuids a weak
alias for geteuids.
* hurd/Versions [GLIBC_2.0]: Add __getuids,
__hurd_file_name_lookup and _hurd_umask.
[GLIBC_2.1]: Add _hurd_proc_init.
* hurd/Makefile [versioning] (routines): Add compat-20.
(shared-only-routines): Likewise.
* hurd/hurdinit.c (_hurd_new_proc_init): Renamed from
_hurd_proc_init. Use it as the default _hurd_proc_init version
for GLIBC_2.1.
* hurd/compat-20.c: New file.
* mach/Versions [GLIBC_2.0]: Add __vm_allocate.
