Upgrade to libxml 2.9.2 and libxslt 1.1.28

third_party/libxml/src/README.tests

Index: third_party/libxml/src/README.tests
diff --git a/third_party/libxml/src/README.tests b/third_party/libxml/src/README.tests
index 66522ab5ec11aeb6a2eba5fb98cb4d0d5e45f691..8d86f2a19ceb0fdbe519f1da7156e5e1308666df 100644
--- a/third_party/libxml/src/README.tests
+++ b/third_party/libxml/src/README.tests
@@ -14,17 +14,26 @@ program has a different testing purpose:
 
 The command:
 
+  make check
+or
   make -f Makefile.tests check
 
 should be sufficient on an Unix system to build and exercise the tests
 for the version of the library installed on the system. Note however
 that there isn't backward compatibility provided so if the installed
-version is older to the testsuite one, failing to compile or run the tests
+version is older than the testsuite one, failing to compile or run the tests
 is likely. In any event this won't work with an installed libxml2 older
 than 2.6.20.
-Building on other platfroms should be a matter of compiling the C files
+
+Building on other platforms should be a matter of compiling the C files
 like any other program using libxml2, running the test should be done
 simply by launching the resulting executables.
 
+Also note the availability of a "make valgrind" target which will run the
+above tests under valgrind to check for memory errors (but this relies
+on the availability of the valgrind command and take far more time to
+complete).
+
 Daniel Veillard
-Thu Jul 24 2008
+Mon May  7 2012
+