Roll libxml to 2.9.3

third_party/libxml/src/libxml2-config.cmake.in

 # libxml2-config.cmake
 # --------------------
 #
 # Libxml2 cmake module.
 # THis module sets the following variables:
 #
 # ::
 #
 #   LIBXML2_INCLUDE_DIRS      - Directory where libxml2 headers are located.
 #   LIBXML2_LIBRARIES         - xml2 libraries to link against.
 #   LIBXML2_VERSION_MAJOR     - The major version of libxml2.
 #   LIBXML2_VERSION_MINOR     - The minor version of libxml2.
 #   LIBXML2_VERSION_PATCH     - The patch version of libxml2.
 #   LIBXML2_VERSION_STRING    - version number as a string (ex: "2.3.4")
 #   LIBXML2_MODULES           - whether libxml2 as dso support
 
 get_filename_component(_libxml2_rootdir ${CMAKE_CURRENT_LIST_DIR}/../../../ ABSOLUTE)
 
 set(LIBXML2_VERSION_MAJOR  @LIBXML_MAJOR_VERSION@)
 set(LIBXML2_VERSION_MINOR  @LIBXML_MINOR_VERSION@)
 set(LIBXML2_VERSION_MICRO  @LIBXML_MICRO_VERSION@)
 set(LIBXML2_VERSION_STRING "@VERSION@")
 set(LIBXML2_INSTALL_PREFIX ${_libxml2_rootdir})
-set(LIBXML2_INCLUDE_DIRS   ${_libxml2_rootdir}/include)
+set(LIBXML2_INCLUDE_DIRS   ${_libxml2_rootdir}/include ${_libxml2_rootdir}/include/libxml2)
 set(LIBXML2_LIBRARY_DIR    ${_libxml2_rootdir}/lib)
 set(LIBXML2_LIBRARIES      -L${LIBXML2_LIBRARY_DIR} -lxml2)
 
 if(@WITH_THREADS@)
   find_package(Threads REQUIRED)
   list(APPEND LIBXML2_LIBRARIES ${CMAKE_THREAD_LIBS_INIT})
 endif()
 
 if(@WITH_LZMA@)
   find_package(LibLZMA REQUIRED)
   list(APPEND LIBXML2_LIBRARIES    ${LIBLZMA_LIBRARIES})
   list(APPEND LIBXML2_INCLUDE_DIRS ${LIBLZMA_INCLUDE_DIRS})
 endif()
 
 if(@WITH_ZLIB@)
   find_package(ZLIB REQUIRED)
   list(APPEND LIBXML2_LIBRARIES    ${ZLIB_LIBRARIES})
   list(APPEND LIBXML2_INCLUDE_DIRS ${ZLIB_INCLUDE_DIRS})
 endif()
 
 list(APPEND LIBXML2_LIBRARIES @ICU_LIBS@ @ICONV_LIBS@ @M_LIBS@ @WIN32_EXTRA_LIBADD@ @LIBS@)
 
 # whether libxml2 has dso support
 set(LIBXML2_MODULES @WITH_MODULES@)
 
 mark_as_advanced( LIBXML2_INCLUDE_DIRS LIBXML2_LIBRARIES )