Okay this is scary but it is just adding a configure option to disable

* HTMLtree.c SAX2.c c14n.c catalog.c configure.in debugXML.c
  encoding.c entities.c nanoftp.c nanohttp.c parser.c relaxng.c
  testAutomata.c testC14N.c testHTML.c testRegexp.c testRelax.c
  testSchemas.c testXPath.c threads.c tree.c valid.c xmlIO.c
  xmlcatalog.c xmllint.c xmlmemory.c xmlreader.c xmlschemas.c
  example/gjobread.c include/libxml/HTMLtree.h include/libxml/c14n.h
  include/libxml/catalog.h include/libxml/debugXML.h
  include/libxml/entities.h include/libxml/nanohttp.h
  include/libxml/relaxng.h include/libxml/tree.h
  include/libxml/valid.h include/libxml/xmlIO.h
  include/libxml/xmlschemas.h include/libxml/xmlversion.h.in
  include/libxml/xpathInternals.h python/libxml.c:
  Okay this is scary but it is just adding a configure option
  to disable output, this touches most of the files.
Daniel
diff --git a/c14n.c b/c14n.c
index 89589ca..620c9a3 100644
--- a/c14n.c
+++ b/c14n.c
@@ -12,6 +12,7 @@
 #define IN_LIBXML
 #include "libxml.h"
 #ifdef LIBXML_C14N_ENABLED
+#ifdef LIBXML_OUTPUT_ENABLED
 
 #ifdef HAVE_STDLIB_H
 #include <stdlib.h>
@@ -1927,4 +1928,5 @@
     *out++ = 0;
     return (buffer);
 }
+#endif /* LIBXML_OUTPUT_ENABLED */
 #endif /* LIBXML_C14N_ENABLED */