Return the size in bytes of a low level file.
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 Syntax

        GT_FSize(<nFileHandle>) --> nSizeInBytes

 Arguments:

      <nFileHandle> is the handle of a file that has been opened or
      created with one of Clipper's low level file functions.

 Returns:

      The size of the file in bytes.

 Description:

      GT_FSize() can be used for finding the size of a file opened with
      Clipper's low level file functions.

 Examples:

      // Print the size of a file.

      local nFile := fopen("LIFE.42")
      ? GT_FSize(nFile)     // Print the size of the file.
      fclose(nFile)

 Source: FSIZE.PRG

 Author:  Dave Pearson