/*
* Allocate a new cluster and chain it onto the end of the file.
*
* dep - the file to extend
* count - number of clusters to allocate
* bpp - where to return the address of the buf header for the first new
* file block
* ncp - where to put cluster number of the first newly allocated cluster
* If this pointer is 0, do not return the cluster number.
* flags - see fat.h
*
* NOTE: This function is not responsible for turning on the DE_UPDATE bit of
* the de_flag field of the denode and it does not change the de_FileSize
* field. This is left for the caller to do.
*/