* sysdeps/generic/sigset-cvt-mask.h (sigset_set_old_mask,
sigset_get_old_mask): Make it work with larger sigset_t.
* sysdeps/posix/sigblock.c (__sigblock): Use those macros.
* sysdeps/posix/sigsetmask.c (__sigsetmask): Likewise.
* sysdeps/posix/sigpause.c (__sigpause): Likewise.