Do not use KERNEL_DIR env var in Makefile.am

A Gentoo user reported an issue where the build system would
attempt to recurse into the kernel source tree if KERNEL_DIR
is set in the environment. KERNEL_DIR is an environment variable
that is used when the kernel sources are in a non-standard
location, so it is necessary to stop relying on it to prevent
this issue.

https://bugs.gentoo.org/show_bug.cgi?id=433946

Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Fix spl_kmem_init_kallsyms_lookup() panic

Due to I/O buffering the helper may return successfully before
the proc handler has a chance to execute.  To catch this case
wait up to 1 second to verify spl_kallsyms_lookup_name_fn was
updated to a non SYMBOL_POISON value.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes zfsonlinux/zfs#699
Closes zfsonlinux/zfs#859
Remove the ChangeLog

The ChangeLog was retired long ago, the git commit logs are
authoritative.  To avoid any confusion remove the ChangeLog.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Refresh AUTHORS

The AUTHORS file was getting stale.  Refresh its contents
using the authors listed in the git commit logs.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
SPL 0.6.0-rc13