MFC r292816,r292818,r292819:

MFC r292816,r292818,r292819:

r292816:

Place cancel and error under #ifdef DEBUG to mute
-Wunused-but-set-variable warnings reported by gcc 4.9

Remove some trailing whitespace as well

Tested with and without -DDEBUG

r292818:

Fix style(9) a bit and ensure that error from initializing kqueue(2) is
sane

- Push the kqueue(2) initialization down so the errno will correspond with
  the failure instead of potentially being stomped on by functions called
  by `PLAIN_REQUIRE_KERNEL_MODULE`
- Delete trailing whitespace
- Add spaces between braces for conditional and control blocks (for/if)
- Use err/errx instead of perror+printf+exit/printf+exit.
- Remove braces for single-line conditionals

Tested with and without -DDEBUG

r292819:

- Fix an improperly sized buffer for `pathname` [1]
- Fix a -Wunused-but-set-variable warning [2]

git-svn-id: svn://svn.freebsd.org/base/stable/10@293140 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f