Add dependency xalan:serializer to all mule-dependency pom's

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The xalan:serializer dependency is in mule/lib/boot but is missing from 
mule-dep's pom's.

The missing dependency show itself as java.lang.NoClassDefFoundError's for some 
cases where other lib's are trying to serialize XML (for example for creating 
SAML tcikets with OpenSAML).

Note: the dependency was added for 3.4.0-dep-pom in r2126 (part of issue 339) 
but wasn't consistenly added to all pom's.

Original issue reported on code.google.com by hakan.dahl@gmail.com on 10 Apr 2014 at 7:11