Increase cutoff for resumable uploads (from 1MB to 64MB).
Increase cutoff for resumable uploads (from 1MB to 64MB).

The previous cutoff was leading to uploads of some files failing
occasionally due to rate limit errors that persisted even after
exponential backoff.  (Presumably since we were issuing more Drive API
calls--one for each chunk uploaded--this hit the rate limits more
quickly.)  This seems to fix that.

google/skicka,clonemeagain/skicka,pnu/skicka