Update to 1.2:

- Use netbsd-*.gz files to install the kernel rather than kern-*.tgz sets.
  This lets sysupgrade work in conjunction with the "releasekernel" target
  of build.sh, as this generates the former instead of the latter.

- Preserve timestamps of the kernel when backing it up as onetbsd.

- Fix some tests to not rely on the current state of the system (the cache
  directory and the autodetection of KERNEL).

(jmmv)