Description
int 
gzseek ( resource zp, int offset )
   Sets the file position indicator for the given file pointer to the
   given offset byte into the file stream. Equivalent to calling (in C)
   gzseek(zp, offset, SEEK_SET).
  
   If the file is opened for reading, this function is emulated but
   can be extremely slow. If the file is opened for writing, only
   forward seeks are supported; gzseek() then compresses
   a sequence of zeroes up to the new starting position.
  
Return Values
   Upon success, returns 0; otherwise, returns -1. Note that seeking
   past EOF is not considered an error.