gfs_pio_getline - read a line
char *gfs_pio_getline (GFS_File f, char * s, size_t size, int * eofp);
gfs_pio_getline() reads a line from the file gf, and stores to the
buffer starting at s at most size - 1 bytes. It is indistinguishable
whether the length of a line is more than size or equal to size - 1.
It sets 1 into the address pointed by eofp on end of file, otherwise it
NULL The function terminated successfully.
Insufficient memory was available.
Others An error except the above occurred. The reason is shown by its