Include precompiled ANTLR 3.5 binaries and always use them.

Instead of trying to build ANTLR from sources from a submodule (and failing most of the time), just include upstream precompiled JAR and the Python runtime module. ANTLR development focuses on v4 anyway, so further updates to v3 are unlikely.

This simplifies use from git checkout, especially on Windows. Should also fix Travis builds.

/cc @vadz