Merge pull request google#28 from mchinen/v310_exp_status_pffft_squashed

[New version V310] 
This PR is quite large and does various things:

Squashes several internal commits that do the following.
Introduces an exponential fit for speech mode. This means the scores will differ when using speech mode, but not audio mode. As a result, the conformance version was bumped to 310, and we will apply a v3.1.0 tag.
Merges internal Status{,Or} changes from @gjasny's PR google#23. In many cases I preferred the internal version even though google#23 had better formatting, because it will be overwritten by the next internal export due to things like alphabetical ordering or different internal namings.
Merges pffft windows and linux repositories