Solve compilation failure due to javadoc on jdk1.8

Add -Xdoclint to avoid compilation failure due to javadoc on java 1.8. See http://blog.joda.org/2014/02/turning-off-doclint-in-jdk-8-javadoc.html for more details.
An important amount of errors comes from :
liquibase-master/liquibase-core/src/main/java/liquibase/util/file/FilenameUtils.java