[trac598] Doxyfile was missing a library

doc/Doxyfile

@@ -572,7 +572,8 @@ INPUT                  = ../src/lib/cc ../src/lib/config ../src/lib/dns \
     ../src/lib/exceptions ../src/lib/datasrc ../src/bin/auth \
     ../src/bin/resolver ../src/lib/bench ../src/lib/log ../src/lib/asiolink/ \
     ../src/lib/nsas ../src/lib/testutils ../src/lib/cache \
-    ../src/lib/server_common/ ../src/bin/sockcreator/ ../src/lib/util/
+    ../src/lib/server_common/ ../src/bin/sockcreator/ ../src/lib/util/ \
+    ../src/lib/resolve
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding, which is