snappy: add a testdata flag to the test.

Also change the base URL for downloading testdata. The upstream C++ snappy
project has moved from code.google.com (svn) to github.com (git).

The actual testdata used also changed in February 2014:
https://github.com/google/snappy/commit/19690d78e83f8963f497585031efa3d9ca66b807

LGTM=dsymonds
R=dsymonds
CC=golang-codereviews
https://codereview.appspot.com/199530043
1 file changed
tree: db1672e3872d7d3b2db04dd8c5ff9ba02c0edccd
  1. lib/
  2. snappy/
  3. .hgignore
  4. AUTHORS
  5. CONTRIBUTORS
  6. LICENSE
  7. README