In particular, pull Go 1.11 to get module support. Also we don't need to
pull in libfuzzer anymore.
Change-Id: I8098f64cef59422d9d43f7eca5bf3ced69eb70c4
Reviewed-on: https://boringssl-review.googlesource.com/31864
Reviewed-by: Adam Langley <agl@google.com>