#10 Add support for mkstemp and fcntl-locking

[Kai Dietrich]

Currently, when you try to run git or rsync on an ftpfs tree, they fail, because mkstemp and fcntl-locking is not implemented in curlftpfs. Of course these operations cannot be implemented safely on a network fs, but with the assumption that only one user operates on the filesystem tree, it should be safe enough for the warned user. So I suggest an option to switch on unsafe local locking/mkstemp emulation.