[krbdev.mit.edu #8474] gnu libc OFD lock bug affects krb5

[Greg Hudson via RT]

In 1.14, we changed krb5_lock_file() to use OFD locks when possible 
(ticket #8023).  Unfortunately, a bug in gnu libc can cause this code to 
fail on 32-bit Linux:

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

This bug does not appear to be fixed.  We can work around it by using 
struct flock64 and fcntl64() in the appropriate circumstances.

This has come up on the Kerberos list (one thread with messages in two 
different months) and in a Debian bug:

http://mailman.mit.edu/pipermail/kerberos/2015-December/021101.html
http://mailman.mit.edu/pipermail/kerberos/2016-August/021351.html
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=834035