Function silc_sftp_read
SYNOPSIS
void silc_sftp_read(SilcSFTP sftp,
SilcSFTPHandle handle,
uint64 offset,
uint32 len,
SilcSFTPDataCallback callback,
void *context);
DESCRIPTION
Reads data from the file indicated by the file handle `handle' starting
from the offset of `offset' at most `len' bytes. The `callback' is
called to return the read data.