This reverts commit 59362c80e3.
This breaks gnulib's autoconf test for POSIX compatibility of
fflush/fseek. After fflush/fseek, ftello and lseek are out of
sync, with lseek having the wrong offset. This breaks backward
compatibility with Cygwin applications.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>