* Fix width in begin list (.Bl) macro.

* Fix width in begin list (.Bl) macro.

* Correct buildworld description.

* Add documentation for the quickworld, realquickworld, crossworld,
  nativekernel, quickkernel, kernel, preupgrade and upgrade targets.

* Remove obsolete documentation for the aout-to-elf, aout-to-elf-build,
  aout-to-elf-install and move-aout-libs targets.

* Remove cross-compiling examples for PC98 and Alpha. Comment out
  two sentences that can go back in when we support different
  architectures.

* Refer to /etc/defaults/make.conf instead of
  /usr/share/examples/etc/defaults/make.conf.

* Remove reference to mergemaster(8).

* Bump date.

Add some changes from FreeBSD's build.7:

* Add reference to config(8).

* Miscellaneous mdoc cleanup.