* hurd/hurdinit.c (_hurd_ports_use): Return error _hurd_ports is null.
* hurd/hurdsig.c (_hurdsig_init): Conditionalize exception port setup
for old CMU and new OSF Mach interface flavors.
* hurd/hurdfault.c (_hurdsig_fault_init): Likewise.
* sysdeps/mach/hurd/fork.c (__fork): Likewise.