hurd: Fix build without NO_HIDDEN

	* posix/sched_primax.c (__sched_get_priority_max): Add
	libc_hidden_def.
	* posix/sched_primin.c (__sched_get_priority_min): Likewise.
	* sysdeps/mach/hurd/mmap.c (__mmap): Likewise.
	* sysdeps/mach/hurd/mmap64.c (__mmap64): Likewise.
	* sysdeps/mach/hurd/mprotect.c (__mprotect): Likewise.
	* sysdeps/mach/hurd/munmap.c (__munmap): Likewise.
	* sysdeps/mach/hurd/dl-sysdep.c (__GI___getpid,
	__GI___strtoul_internal, __GI_____strtoul_internal, __GI___chk_fail,
	__GI___fortify_fail, __GI___assert_fail, __GI___assert_perror_fail):
	Add aliases.