Use makefile variables rather than hard-coded paths for $sbindir.
Rework the .zfs code.
Allow .zfs even if hidden
Use full path to zfs command in the autoimport script.
Stop redefining zfs_sleep_until.

ZOL introduced zfs_delay.h for the kernel context only. Move our
kernel version of zfs_sleep_until into zfs_delay.h, and do not
include zfs_delay.h in zfs_context_userland.h.

Also, just as ZOL does, we can use nanosleep in our userland context.
add declaration for mach_vm_pressure_monitor
Remove two old debug panics from avl.c
Define the custom-icon constants only once
Fix a Wparentheses warning
Remove defunct zfs_get_snapused_int()

zfs_get_snapused_int() was replaced with lzc_snaprange_space() in
https://github.com/illumos/illumos-gate/commit/4445fffbbb1ea25fd0e9ea68b9380dd7a6709025
Fix three Wimplicit-function-declaration warnings in spa.c

libkern/OSKextLib.h has the declarations for OSKextRetainKextWithLoadTag,
OSKextGetCurrentLoadTag, and OSKextReleaseKextWithLoadTag.
Restore declaration of zfs_zevent_fd_hold

Now that zfs_zevent_fd_hold has been ported, its declaration should
not be commented out in the header.
Eliminate Wimplicit-function-declaration for cv_wait_io() in userland context.
Replace deprecated vsprintf with vsnprintf in log_internal()
Make the check for Core Storage LV more forgiving.
Use getcpuid from spl for kernel context.
Move KERNEL_MODPREFIX to ZFS_AC_CONFIG_ALWAYS.

Always configure KERNEL_MODPREFIX because --with-config=user needs
it in order to know where to find the custom volume icon.
Fix vnode iocount holds in ctldir, release holds on error case.
Mahrens confirmed we do not need to release holds in error cases.
Merge commit '4afe1f31aa0a2813e92af5c1cf0624dc4f1c47ed' into pathfix

Conflicts:
scripts/zpool-autoimport.sh.in