Remove 'MDATA_USE_SIZE' unused config constant

#define MDATA_USE_GID false

#define MDATA_USE_LINK_CNT false

#define MDATA_USE_BLOCKS false

#define MDATA_USE_SIZE true // XXX to be added in ADAFS_DATA. currently on by default

// should permissions be checked when access() is called or discarded (disabled by default)

//#define CHECK_ACCESS