Bug#657835: libc6: libc deadlocks in child process after fork

[Max Dmitrichenko <dmitrmax@gmail.com>]

This is the stack trace of a deadlocked child:

#0  __lll_lock_wait_private () at
../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:97
#1  0x000000346929c08d in _L_lock_2164 () at tzset.c:138
#2  0x000000346929be47 in __tz_convert (timer=0x346959da74,
use_localtime=0, tp=0x7f7a25211990) at tzset.c:619
#3  0x00007f7a2a1ff2a0 in DateTime::now () at Sources/DateTime.cpp:174