Misc improvements to the ZFS test suite

zfs/tests/cli_root/zpool_clear/zpool_clear_001_pos.ksh
Make the outlines of some parts of this test more obvious.

zfs/include/libtest.kshlib
zfs/tests/hotspare/hotspare_detach_001_pos.ksh
Simplify test for "did the pool resilver happen?"

zfs/include/Makefile
Specify variables with variables, and not immediately after targets.

zfs/bin/Makefile
Style: expand variable assignments across multiple lines

Submitted by: Will
Sponsored by: Spectra Logic Corp