Bug#818787: doxygen: Changes default HAVE_DOT to YES without having graphviz in the Depends line.

[Santiago Vila]

I believe the attached patch is closer to the "right" fix.

Presumably, packages actually requiring the dot command will have an
override for this variable in their Doxyfiles.

Thanks.
--- a/src/config.xml
+++ b/src/config.xml
@@ -3104,7 +3104,7 @@ where `loc1` and `loc2` can be relative or absolute paths 
or URLs.
     </option>
   </group>
   <group name='Dot' docs='Configuration options related to the dot tool'>
-    <option type='bool' id='CLASS_DIAGRAMS' defval='1'>
+    <option type='bool' id='CLASS_DIAGRAMS' defval='0'>
       <docs>
 <![CDATA[
  If the \c CLASS_DIAGRAMS tag is set to \c YES, doxygen will