release 2017-01-01

Make SimplifyWalker::SimplifyRepeat() use Regexp::Concat().

This builds a two-level tree for very large numbers of
subexpressions. When min is greater than 65535 due to
coalescing, for example.

This bug was discovered by the LLVM fuzzer.

Change-Id: I7e21d24f6546b9d8f3a3d844e0ed5c6af246aa1e
Reviewed-on: https://code-review.googlesource.com/9890
Reviewed-by: Paul Wankadia <junyer@google.com>