VReadData - reads a 3DVIEWNIX 1.0 data file.
  VReadData(data, size, items, fp, items_read)
  char *data;                           /*RETURN*/
  int size,items,
  FILE *fp;
  int *items_read;                      /*RETURN*/
  VReadData reads a 3DVIEWNIX data file. VReadData reads a string of
bytes into an array from the specified file pointer. VReadData assumes that
fp points to the beginning of the data part, and that the data in the file
follows the big endian format for short (size 2) and integer (size 4) values.
VReadData reads the data, converts it to the format supported by the server
and returns the number of items read in the item_read field.
Return Value
  0 - work successfully.
  2 - read error.
  5 - improper seeks.
  100 - incorrect 3DVIEWNIX file header.
  data - the array where the function puts the string of bytes.
  size - size of each data item. Valid items are 1, 2 & 4.
  items- the number of items to be read.
  fp - a pointer to the input data file.
  items_read- returns the number of items actually read.
Side Effects
  VReadData can read only 1, 2 or 4 byte integer data. This will be expanded
to handle floating point data.
Entry Conditions
  If the fp, data, or items_read is NULL, or items is zero, or size is not 1,
2 or 4, VReadData prints an error message to the standard error stream,
produces a core dump file, and exits from the current process.
Related Functions
VGetHeaderLength, VCloseData, VWriteData, VSeekData.