Updates to X configuration section for a non-HAL universe

[dru]

Summary

Beginning of edits to X chapter now that HAL is no longer required. Note that I shuffled some stuff and nuked others, but did not write any new material. The patch, once complete, will address https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=197411.

Test Plan

Basically, make sure commit is sanity-checked:

1. Are any required steps missing?

2. Is any of the remaining stuff deprecated? For example, is the Ctrl+Alt+Backspace note still needed or relevant?

3. Are any of the Caveats deprecated?

[wblock]

All of the parts about generating a config file and testing it should be moved to a later section. In many versions of FreeBSD, the system will appear to have locked up after they exit the X test because vt(4) is not running.

chapter.xml

291

Avoid the informal "you". Actually, this whole paragraph is kind of redundant, the first three sentences are all suggesting the same thing.

<application>&xorg;</application> can automatically detect and configure itself for most hardware without a configuration file.

Do we need to tell the reader to save the old file first? And if we do, should we even mention /etc/X11/xorg.conf, when the correct location on FreeBSD is /usr/local/etc/X11/xorg.conf?