[PHP-INST] fix for problem with configure script libxml

[Jon Wagoner]

A machine I was installing on had both libxml and libxml2.  In the configure script 
test, it has:
 
  if test -r $PHP_DOM/include/libxml/tree.h; then
    DOMXML_DIR=$PHP_DOM
  elif test -r $PHP_DOM/include/libxml2/libxml/tree.h; then
    DOMXML_DIR=$PHP_DOM
    DOMXML_DIR_ADD="/libxml2"

Since it found libxml first, it said I needed a later version.  I changed it to look 
for libxml2 first, since that should be newer, and it works fine:
 
  if test -r $PHP_DOM/include/libxml2/libxml/tree.h; then
    DOMXML_DIR=$PHP_DOM
    DOMXML_DIR_ADD="/libxml2"
  elif test -r $PHP_DOM/include/libxml/tree.h; then
    DOMXML_DIR=$PHP_DOM
 
Jon