fix for CVE-2008-4226, a memory overflow when building gigantic text

* SAX2.c parser.c: fix for CVE-2008-4226, a memory overflow
  when building gigantic text nodes, and a bit of cleanup
  to better handled out of memory problem in that code.
* tree.c: fix for CVE-2008-4225, lack of testing leads to
  a busy loop test assuming one have enough core memory.
Daniel

svn path=/trunk/; revision=3803
diff --git a/parser.c b/parser.c
index 4b7b758..c52d360 100644
--- a/parser.c
+++ b/parser.c
@@ -4142,6 +4142,9 @@
                     line = ctxt->input->line;
                     col = ctxt->input->col;
 		}
+                /* something really bad happened in the SAX callback */
+                if (ctxt->instate != XML_PARSER_CONTENT)
+                    return;
 	    }
 	    ctxt->input->cur = in;
 	    if (*in == 0xD) {
@@ -4222,6 +4225,9 @@
 		}
 	    }
 	    nbchar = 0;
+            /* something really bad happened in the SAX callback */
+            if (ctxt->instate != XML_PARSER_CONTENT)
+                return;
 	}
 	count++;
 	if (count > 50) {