Do not look for Content-Length in headers and try to convert them into
integer representations use ContentLength field from *http.Request*.
If Content-Length is understood to be as '-1' then treat it as an error
condition, since it could be a malformed body to crash the server.
Fixes#1011
Put() replies back with
- EntityTooLarge with > 5GB in single PUT operation
- EntityTooSmall with < 1B in single PUT operation
- IncompleteBody with ho Content-Length found in HTTP request header