Update porters-handbook for USES=gnome

[kwm]

Summary

Draft for documenting USES=gnome in the porters-handbook. The part in
using-gnome needs more work but I'm blanking atm.

I put a blob in the start of the page about needing USES=gnome, instead of
rewriting text all over the place to take into account that USES=gnome needs
to be added too. Currently the USES=gnome uses a <programlisting> but that
looks ugly to me, it breaks up the text in bad ways (in my eyes). Maybe
use <literaly> instead? I'm open for some expert suggestions.

And the summary is more text then the actualy diff, yay me....

Test Plan

http://rainbow-runner.nl/freebsd-doc/en_US.ISO8859-1/books/porters-handbook/uses-gnome.html
http://rainbow-runner.nl/freebsd-doc/en_US.ISO8859-1/books/porters-handbook/using-gnome.html

[wblock]

en_US.ISO8859-1/books/porters-handbook/special/chapter.xml

1425

Does this title need to change to reflect that USE_GNOME is now USES=gnome?

1429

Embedding a programlisting inside a para does not work too well. Instead, split the para. Also, "needs to be" seems like it is probably hard to translate. So maybe this: (indenting not shown)

<para>The functionality provided by
<filename>Mk/Uses/gnome.mk</filename> is enabled by
adding <literal>gnome</literal> to the <varname>USES</varname>
values:</para>

<programlisting>USES=gnome</programlisting>

<para>This document assumes the variable has been set and will not mention it again.</para>

1430

Avoid contractions.

1431

Open and close para tags go on the same line as content.

1436

The second mention of the path is redundant, it can just say:

The added code supplies the needed

1437

Needs a serial comma after "run-time".

1440

Another USE_GNOME that seems like it should be changed.

en_US.ISO8859-1/books/porters-handbook/uses/chapter.xml

579

s/macro's/macros/
USE_GNOME, INSTALLS_ICONS, and GLIB_SCHEMAS need markup, maybe <literal>?

580

The link can just be an <xref> and will show the correct link name.

[mat]

en_US.ISO8859-1/books/porters-handbook/special/chapter.xml

1429

Or use <literal>USES=gnome</literal>.