libxml2: add Debian patches to address CVEs

Debian uses libxml2 2.9.4 in Stretch. This adds their security related
fixes from 2.9.4+dfsg1-2.2+deb9u2 to LEDE's 17.01 release.

Fixed CVEs:

CVE-2016-4658
CVE-2016-5131
CVE-2017-0663
CVE-2017-15412
CVE-2017-7375
CVE-2017-7376
CVE-2017-9047
CVE-2017-9048
CVE-2017-9049
CVE-2017-9050

Signed-off-by: Sebastian Kemper <sebastian_ml@gmx.net>

libs/libxml2/patches/0005-Fix-XPointer-paths-beginning-with-range-to.patch

@@ -0,0 +1,138 @@
+From 9ab01a277d71f54d3143c2cf333c5c2e9aaedd9e Mon Sep 17 00:00:00 2001
+From: Nick Wellnhofer <wellnhofer@aevum.de>
+Date: Tue, 28 Jun 2016 14:22:23 +0200
+Subject: [PATCH] Fix XPointer paths beginning with range-to
+
+The old code would invoke the broken xmlXPtrRangeToFunction. range-to
+isn't really a function but a special kind of location step. Remove
+this function and always handle range-to in the XPath code.
+
+The old xmlXPtrRangeToFunction could also be abused to trigger a
+use-after-free error with the potential for remote code execution.
+
+Found with afl-fuzz.
+
+Fixes CVE-2016-5131.
+---
+ result/XPath/xptr/vidbase | 13 ++++++++
+ test/XPath/xptr/vidbase   |  1 +
+ xpath.c                   |  7 ++++-
+ xpointer.c                | 76 ++++-------------------------------------------
+ 4 files changed, 26 insertions(+), 71 deletions(-)
+
+--- a/xpath.c
++++ b/xpath.c
+@@ -10691,13 +10691,18 @@ xmlXPathCompPathExpr(xmlXPathParserConte
+ 		    lc = 1;
+ 		    break;
+ 		} else if ((NXT(len) == '(')) {
+-		    /* Note Type or Function */
++		    /* Node Type or Function */
+ 		    if (xmlXPathIsNodeType(name)) {
+ #ifdef DEBUG_STEP
+ 		        xmlGenericError(xmlGenericErrorContext,
+ 				"PathExpr: Type search\n");
+ #endif
+ 			lc = 1;
++#ifdef LIBXML_XPTR_ENABLED
++                    } else if (ctxt->xptr &&
++                               xmlStrEqual(name, BAD_CAST "range-to")) {
++                        lc = 1;
++#endif
+ 		    } else {
+ #ifdef DEBUG_STEP
+ 		        xmlGenericError(xmlGenericErrorContext,
+--- a/xpointer.c
++++ b/xpointer.c
+@@ -1332,8 +1332,6 @@ xmlXPtrNewContext(xmlDocPtr doc, xmlNode
+     ret->here = here;
+     ret->origin = origin;
+ 
+-    xmlXPathRegisterFunc(ret, (xmlChar *)"range-to",
+-	                 xmlXPtrRangeToFunction);
+     xmlXPathRegisterFunc(ret, (xmlChar *)"range",
+ 	                 xmlXPtrRangeFunction);
+     xmlXPathRegisterFunc(ret, (xmlChar *)"range-inside",
+@@ -2243,76 +2241,14 @@ xmlXPtrRangeInsideFunction(xmlXPathParse
+  * @nargs:  the number of args
+  *
+  * Implement the range-to() XPointer function
++ *
++ * Obsolete. range-to is not a real function but a special type of location
++ * step which is handled in xpath.c.
+  */
+ void
+-xmlXPtrRangeToFunction(xmlXPathParserContextPtr ctxt, int nargs) {
+-    xmlXPathObjectPtr range;
+-    const xmlChar *cur;
+-    xmlXPathObjectPtr res, obj;
+-    xmlXPathObjectPtr tmp;
+-    xmlLocationSetPtr newset = NULL;
+-    xmlNodeSetPtr oldset;
+-    int i;
+-
+-    if (ctxt == NULL) return;
+-    CHECK_ARITY(1);
+-    /*
+-     * Save the expression pointer since we will have to evaluate
+-     * it multiple times. Initialize the new set.
+-     */
+-    CHECK_TYPE(XPATH_NODESET);
+-    obj = valuePop(ctxt);
+-    oldset = obj->nodesetval;
+-    ctxt->context->node = NULL;
+-
+-    cur = ctxt->cur;
+-    newset = xmlXPtrLocationSetCreate(NULL);
+-
+-    for (i = 0; i < oldset->nodeNr; i++) {
+-	ctxt->cur = cur;
+-
+-	/*
+-	 * Run the evaluation with a node list made of a single item
+-	 * in the nodeset.
+-	 */
+-	ctxt->context->node = oldset->nodeTab[i];
+-	tmp = xmlXPathNewNodeSet(ctxt->context->node);
+-	valuePush(ctxt, tmp);
+-
+-	xmlXPathEvalExpr(ctxt);
+-	CHECK_ERROR;
+-
+-	/*
+-	 * The result of the evaluation need to be tested to
+-	 * decided whether the filter succeeded or not
+-	 */
+-	res = valuePop(ctxt);
+-	range = xmlXPtrNewRangeNodeObject(oldset->nodeTab[i], res);
+-	if (range != NULL) {
+-	    xmlXPtrLocationSetAdd(newset, range);
+-	}
+-
+-	/*
+-	 * Cleanup
+-	 */
+-	if (res != NULL)
+-	    xmlXPathFreeObject(res);
+-	if (ctxt->value == tmp) {
+-	    res = valuePop(ctxt);
+-	    xmlXPathFreeObject(res);
+-	}
+-
+-	ctxt->context->node = NULL;
+-    }
+-
+-    /*
+-     * The result is used as the new evaluation set.
+-     */
+-    xmlXPathFreeObject(obj);
+-    ctxt->context->node = NULL;
+-    ctxt->context->contextSize = -1;
+-    ctxt->context->proximityPosition = -1;
+-    valuePush(ctxt, xmlXPtrWrapLocationSet(newset));
++xmlXPtrRangeToFunction(xmlXPathParserContextPtr ctxt,
++                       int nargs ATTRIBUTE_UNUSED) {
++    XP_ERROR(XPATH_EXPR_ERROR);
+ }
+ 
+ /**