Log message:
Bump to 0.15.2 because a fix for MULTIPLE_KERNELS (there was a typo:
-f rather than ! -f, so the test was inverted) was done by hauke.

Log message:
Only complain about a missing kernel config file if we did actually
_not_ find it.

Log message:
Put build actions into a do-build target.  Keep do-install as a pure
"install stuff I already built" step.

Also remove an unnecessary creation of ${PREFIX}/share/mklivecd which
is already handled in INSTALLATION_DIRS.

Log message:
Erm... it's KERNEL_VARS not KERNEL_ARGS.

Log message:
do_conf_reset(): add missing KERNEL_VARS.

Log message:
Fix previous, only check for kernel config and not for the work
directory... which might not be created yet.

Log message:
Do the same for MULTIPLE_KERNELS, check if the kernel is found in
~/.mklivecd before showing informative messages.

Log message:
* Check if the kernel is available in ~/.mklivecd before showing
  informative messages.
* Remove unnecessary checks for USE_GNU_GRUB, now that some options
  are checked to have correct values.
* Misc cleanups.

Log message:
Remove a check for USE_GNU_GRUB, now that there's a common function
to test the value in options.

Log message:
* Check if the option is set, and error out if not.
* Added PERSONAL_CONFIG to the yesno options checks.