fixed problem in xmlTextWriterVSprintf caused by misuse of vsnprintf added

* xmlwriter.c: fixed problem in xmlTextWriterVSprintf caused by
  misuse of vsnprintf
* configure.in, config.h.in: added a configuration check for
  va_copy and added a define for VA_COPY for xmlwriter.c fix
* parser.c: fixed problem with CRLF split between chunks (bug
  #319279) (fix provided by Brion Vibber)
5 files changed