Add support for new (3.0.11+) swigs

Summary:
A change in swig 3.0.9 has caused it to generate modules incompatible
with us using them as __init__.py (bug #769). Swig 3.0.11 adds a setting to help
fix this problem, so use that. Support for older versions of swig remains
unaffected.

Reviewers: zturner

Subscribers: lldb-commits

Differential Revision: https://reviews.llvm.org/D33409

llvm-svn: 303627