Log Message:
Update to 2.4.23.
Changes since 2.4.21:
* performances patches: Peter Jacobi
* c14n fixes, testsuite and performances: Aleksey Sanin
* added xmlDocFormatDump: Chema Celorio
* new tutorial: John Fleck
* new hash functions and performances: Sander Vesik, portability fix
  from Peter Jacobi
* a number of bug fixes: XPath (William Brack, Richard Jinks), XML and
  HTML parsers, ID lookup function
* removal of all remaining sprintf: Aleksey Sanin
* a number of bug fixes: configure scripts, base handling, parser, memory
  usage, HTML parser, XPath, documentation (Christian Cornelssen),
  indentation, URI parsing
* Optimizations for XMLSec, fixing and making public some of the network
  protocol handlers (Aleksey)
* performance patch from Gary Pennington
* Charles Bozeman provided date and time support for XML Schemas datatypes