Xerces version changed

[thomasfruehwirth]

Xerces version changed from 3.1.1 to 3.1.2. Thus, the correct command to get Xerces is

wget http://apache.mirrors.pair.com//xerces/c/3/sources/xerces-c-3.1.2.tar.gz

instead of

wget http://apache.mirrors.pair.com//xerces/c/3/sources/xerces-c-3.1.1.tar.gz