Open a file for writing while enforcing quota
int Ns_OpenWriteWithQuota( char *hServer, char *filename, int mode )
This function opens a file for writing. It returns -1 if an error was encountered, or a file descriptor if successful. If there's an error and errno=0, then an invalid server handle was passed. If the file already exists, it is truncated, and the quota is reduced by the size of that file.