Check that haddock docs build completed before uploading (fixes #119).

[komadori]

I've created a patch which extends the existing checks in BuildClient.hs:buildPackage to check that the desired-package-name.haddock file exists in the output before uploading docs.tar. The existing check was insufficient and allowed hackage-build to upload docs even when the package has failed to build, provided that at least one dependency succeeded. This fixes issue #119 insofar as hackage-build should stop uploading bad docs.

[dcoutts]

Thanks. Though I'm still concerned about the doc tarballs containing many more files that necessary. Is that still the case? Also, are we generating the hoogle .txt files?

[komadori]

Yes, it's still the case that the docs tar-ball contains unused documentation for dependencies and I created issue #130 to track the resolution of that problem. I plan to fix that too if no one else does first, but I haven't got around to it yet. I don't think any Hoogle databases are generated as I don't see them in the tarball and the build client doesn't appear to pass the --hoogle option to Haddock.