Spring cleanup ...: - configure.in Makefile.am config.h.in

Spring cleanup ...:
- configure.in Makefile.am config.h.in xmlversion.h.in: detect if
  we need string functions
- trio.[ch] strio.[ch]: embedded the Trio-0.23 string functions
  to be able to use them where needed. Applied some changes
  to reduce name linking pollution and compile in only what's
  needed.
- HTMLtree.c debugXML.c entities.c error.c nanoftp.c valid.c
  xlink.c xmlversion.h.in xpath.c: got rid of the #ifdef
  for the string manipulation functions
- xmlmemory.[ch]: removed DEBUG_MEMORY_FREED and added it automatically
  to the free() function of xmlmemory.c
- entities.c HTMLtree.c parserInternals.c tree.c uri.c valid.c
  xinclude.c xmlIO.c xpath.c xpointer.c: removed the MEM_CLEANUP
  usage.
Daniel
diff --git a/xmlmemory.c b/xmlmemory.c
index 1cbeca2..d693ba3 100644
--- a/xmlmemory.c
+++ b/xmlmemory.c
@@ -283,9 +283,12 @@
 xmlMemFree(void *ptr)
 {
     MEMHDR *p;
+    char *target;
 
     TEST_POINT
 
+    target = (char *) ptr;
+
     p = CLIENT_2_HDR(ptr);
     if (p->mh_tag != MEMTAG) {
        Mem_Tag_Err(p);
@@ -293,6 +296,7 @@
     }
     p->mh_tag = ~MEMTAG;
     debugMemSize -= p->mh_size;
+    memset(target, -1, p->mh_size);
 
 #ifdef MEM_LIST
     debugmem_list_delete(p);