Work around glibc OFD lock bug on 32-bit Linux

A bug in Gnu libc causes OFD locking to fail unpredictably on 32-bit
Linux, typically leading to deadlocks.  Work around this bug by using
the fcntl64 system call and struct flock64.

See also: https://sourceware.org/bugzilla/show_bug.cgi?id=20251

https://github.com/krb5/krb5/commit/65110210b75d38908cdd84cb202cf013ccf6ed0e
Author: Greg Hudson <ghudson@mit.edu>
Commit: 65110210b75d38908cdd84cb202cf013ccf6ed0e
Branch: master
 src/lib/krb5/os/lock_file.c |   26 ++++++++++++++++++++++++--
 1 files changed, 24 insertions(+), 2 deletions(-)