THRIFT-262. java: Generate Javadocs for library classes

THRIFT-262. java: Generate Javadocs for library classes

This patch adds a 'javadoc' Ant target, and installs the documentation to ${docdir}/thrift/java (/usr/local/share/doc/thrift/java with the default invocation of configure). It also fixes a few Javadoc warnings in the source code.

It also modifies the 'dist' target to include the Java sources in the jar file, so that Eclipse may show the javadocs for Thrift classes automatically (this increases the size of libthrift.jar from 90 Kb to 155 Kb).

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@756603 13f79535-47bb-0310-9956-ffa450edef68