[php-maint] Bug#831739: undefined symbol "php_XML_SetUserData" in plugin shared library wddx.so

[J G Miller]

Concerning the undefined symbol "php_XML_SetUserData" in /usr/lib/php/20151012/wddx.so,
this symbol "php_XML_SetUserData" appears to be defined in /usr/lib/php/20151012/xml.so

Therfore the plugin wddx must be loaded after the plugin xml.so

The Debian configuration priority for xml and wddx are apparently both set to 20, so
that in the conf.d directories of symbolic links, the alphabetic/alphanumeric listing
result in wddx being loaded before xml.

Therefore the solutio to the problem is to assign a lower priority (30 say) to wddx
so that wddx appears after xml in the alphabetic/alphanumeric listing of the conf.d
directories of symbolic links.

In some previous versions, did xml.ini in fact have a priority of 15 to ensure
that this problem did not occur?