Remove ANTLR submodule.
Import ANTLR 3.5.1 binary and Python runtime.
Update code to use precompiled ANTLR.
Merge branch 'antlr-3.5'

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.