Rename typedef to dvr

// The "dvr_vsync_client" structure wraps a client connection to the

// system vsync service. It is used to synchronize application drawing

// with the scanout of the display.

typedef struct dvr_vsync_client dreamos_vsync_client;

typedef struct dvr_vsync_client dvr_vsync_client;

// Creates a new client to the system vsync service.

dvr_vsync_client* dvr_vsync_client_create();