Upgrade to libxml 2.9.2 and libxslt 1.1.28

third_party/libxml/src/INSTALL.libxml2

+Extracted from the documentation:
+   http://xmlsoft.org/FAQ.html#Compilatio
+
+See also the generic INSTALL file for configure options
+
+Compilation
+
+   1.What is the process to compile libxml ? 
+
+     As most UNIX libraries libxml follows the "standard":
+
+     gunzip -c xxx.tar.gz | tar xvf -
+
+     cd libxml-xxxx
+
+     ./configure --help
+
+     to see the options, then the compilation/installation proper
+
+     ./configure [possible options]
+
+     make
+
+     make install
+
+     At that point you may have to rerun ldconfig or similar utility to
+     update your list of installed shared libs.
+
+     At this point you can check that the library is properly functionning
+     by running
+
+     make tests
+
+   2.What other libraries are needed to compile/install libxml ? 
+
+     Libxml does not requires any other library, the normal C ANSI API
+     should be sufficient (please report any violation to this rule you
+     may find).
+
+     However if found at configuration time libxml will detect and use
+     the following libs:
+
+         libz: a highly portable and available widely compression library 
+             http://www.info-zip.org/pub/infozip/zlib/
+         iconv: a powerful character encoding conversion library. It's
+             included by default on recent glibc libraries, so it doesn't
+             need to be installed specifically on linux. It seems it's
+             now part of the official UNIX specification. Here is one
+             implementation of the library which source can be found here.
+             http://clisp.cons.org/~haible/packages-libiconv.html
+             ftp://ftp.ilog.fr/pub/Users/haible/gnu/
+
+   3.make tests may fail on some platforms 
+
+     Sometime the regression tests results don't completely match the
+     value produced by the parser, and the makefile uses diff to print
+     the delta. On some platforms the diff return breaks the compilation
+     process, if the diff is small this is probably not a serious problem
+
+Daniel
+veillard@redhat.com