When the errno is ERRNO_ERROR_STRING it means the error string is a
valid string with the error, and it should not be overwritten with
the HTTP reason_phrase

Fixes https://github.com/owncloud/mirall/issues/1088

Resetting this in trivial helper functions leads to the fact that
error conditions happening in functions calling these helpers get
lost which should not happen.

Bug owncloud/mirall#779 reports about continous upload of files
even though nothing has changed. Logfiles show the fact that the
inode on windows is not reliable for this. Disabled as a result
to fix bug #779.

If the server does not acknowledge the transfer with sending back an
ETag after the last missing chunk was uploaded, this is an error
which is now reported by this new error type.

Fixes https://github.com/owncloud/mirall/issues/1010

In case of NE_TIMEOUT the request is repeated for three times. In this
case, the hooks weren't correctly unhooked which caused a crash.

Patch by Sandro Knauß <buggs@sandroknauss.de>

Fixes Mirall issue #991

Lintian complains about the wrong spelling for transferred

Patch by Sandro Knauß <bugs@sandroknauss.de>

Fixes Mirall issue #990