Please describe the problem:
While compiling PHP 4(.4.1-dev) with the following configure line:
'./configure' \
'--with-apache=/dat/dev/php/apache_1.3.31' '--with-mysql=/usr'
'--with-config-file-path=/etc/httpd' '--enable-track-vars'
'--enable-memory-limit' '--with-mcrypt' '--with-dom' '--enable-debug' 
'--with-gd' '--with-jpeg-dir=/usr' '--with-xpm-dir=/usr'
'--with-freetype-dir=/user' '--with-ctype' '--with-iconv' '--enable-iconv'
'--with-xmlrpc' '--with-pgsql=/usr/lib/postgresql/7.4/bin' '--enable-shmop'
'--enable-sockets' '--enable-sysvsem' '--enable-sysvshm' '--enable-wddx'
'--with-zlib' '--enable-exif' '--enable-cli' '--with-crack' '--enable-mbstring' 
'--with-mbstring' '--disable-zend-memory-manager'

The compile fails with:
In file included from /dat/dev/php/php-4.4dev/ext/wddx/php_wddx.h:26,
                 from main/internal_functions.c:53:
/dat/dev/php/php-4.4dev/ext/xml/expat/expat.h:894: error: redeclaration of
enumerator 'XML_FEATURE_UNICODE'
/usr/include/libxml2/libxml/parser.h:1196: error: previous definition of
'XML_FEATURE_UNICODE' was here
make: *** [main/internal_functions.lo] Error 1

This was working fine in versions previous to 2.6.21.


Steps to reproduce:
1. Comfigure with configure line above
2. Type "make"


Actual results:
The compile fails with:
In file included from /dat/dev/php/php-4.4dev/ext/wddx/php_wddx.h:26,
                 from main/internal_functions.c:53:
/dat/dev/php/php-4.4dev/ext/xml/expat/expat.h:894: error: redeclaration of
enumerator 'XML_FEATURE_UNICODE'
/usr/include/libxml2/libxml/parser.h:1196: error: previous definition of
'XML_FEATURE_UNICODE' was here

Expected results:
No compile error.

Does this happen every time?
Yes.

Other information:
No, except "good luck" ;-)