added xmlMallocAtomic() to be used when allocating blocks which do not

* DOCBparser.c HTMLparser.c c14n.c catalog.c encoding.c globals.c
  nanohttp.c parser.c parserInternals.c relaxng.c tree.c uri.c
  xmlmemory.c xmlreader.c xmlregexp.c xpath.c xpointer.c
  include/libxml/globals.h include/libxml/xmlmemory.h: added
  xmlMallocAtomic() to be used when allocating blocks which
  do not contains pointers, add xmlGcMemSetup() and xmlGcMemGet()
  to allow registering the full set of functions needed by
  a garbage collecting allocator like libgc, ref #109944
Daniel

xmlreader.c

@@ -2633,7 +2633,7 @@ xmlTextReaderBuildMessage(const char *msg, va_list ap) {
     char *larger;
     char *str;
 
-    str = (char *) xmlMalloc(150);
+    str = (char *) xmlMallocAtomic(150);
     if (str == NULL) {
 	xmlGenericError(xmlGenericErrorContext, "xmlMalloc failed !\n");
         return NULL;