Document -dynload flag. Also add it and -shared to the flags reference.

docs/users_guide/flags.xml

@@ -1720,6 +1720,12 @@
 	    </row>
 	  </thead>
 	  <tbody>
+	    <row>
+  	      <entry><option>-shared</option></entry>
+	      <entry>Generate a shared library (as opposed to an executable)</entry>
+	      <entry>dynamic</entry>
+	      <entry>-</entry>
+	    </row>
 	    <row>
 	      <entry><option>-fPIC</option></entry>
 	      <entry>Generate position-independent code (where available)</entry>
@@ -1732,6 +1738,13 @@
 	      <entry>static</entry>
 	      <entry>-</entry>
 	    </row>
+	    <row>
+	      <entry><option>-dynload</option></entry>
+	      <entry>Selects one of a number of modes for finding shared
+	        libraries at runtime.</entry>
+	      <entry>static</entry>
+	      <entry>-</entry>
+	    </row>
 	    <row>
 	      <entry><option>-framework</option> <replaceable>name</replaceable></entry>
 	      <entry>On Darwin/MacOS X only, link in the framework <replaceable>name</replaceable>.

docs/users_guide/phases.xml

@@ -863,6 +863,19 @@ $ cat foo.hspp</screen>
         </listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term>
+          <option>-dynload</option>
+          <indexterm><primary><option>-dynload</option></primary></indexterm>
+        </term>
+        <listitem>
+          <para>
+	    This flag selects one of a number of modes for finding shared
+	    libraries at runtime. See <xref linkend="finding-shared-libs"/> for
+	    a description of each mode.
+          </para>
+        </listitem>
+      </varlistentry>
 
       <varlistentry>
         <term>