Porter's handbook: document the LEGAL_TEXT variable.

Document the LEGAL_TEXT variable which was recently committed
Further explain each of the columbs of /usr/ports/LEGAL.

en_US.ISO8859-1/books/porters-handbook/book.xml

@@ -5457,7 +5457,8 @@ PORTVERSION=	1.0</programlisting>
     </sect1>
 
     <sect1 xml:id="porting-restrictions">
-      <title>Ports with Distribution Restrictions</title>
+      <title>Ports with Distribution Restrictions or Legal
+	Concerns</title>
 
       <para>Licenses vary, and some of them place restrictions on how
 	the application can be packaged, whether it can be sold for
@@ -5567,10 +5568,29 @@ PORTVERSION=	1.0</programlisting>
 	  it is empty.  If only some of the distribution files are
 	  restricted, then set this variable to list them.</para>
 
-	<para>Note that the port committer should add an entry to
-	  <filename>/usr/ports/LEGAL</filename> for every listed
-	  distribution file, describing exactly what the restriction
-	  entails.</para>
+      </sect2>
+
+      <sect2>
+	<title><varname>LEGAL_TEXT</varname></title>
+
+	<para>If the port has legal concerns not addressed by the
+	  above variables, the variable <varname>LEGAL_TEXT</varname>
+	  should be set to a string explaining the concern.  For
+	  example, if special permission was obtained for &os; to
+	  redistribute the binary, this variable should indiate
+	  so.</para>
+      </sect2>
+
+      <sect2>
+	<title><filename>/usr/ports/LEGAL</filename> and
+	  <varname>LEGAL</varname></title>
+
+	<para>A port which sets any of the above variables must also
+	  be added to <filename>/usr/ports/LEGAL</filename>.  The
+	  first column is a glob which matches the restricted
+	  distfiles.  The second column is the port's origin.  The
+	  third column is the output of
+	  <command>make -VLEGAL</command>.</para>
       </sect2>
 
       <sect2>