[Bug-readline] Segfault when pressing down-key

[Jonas Møller]

The error occurred when i pressed the down key twice before a single 
quote at the prompt.

It seems to be an error with readline, I'm sorry that I can't come up 
with any
fix myself, I have very little experience with the ipython and libreadline
codebases.

Kernel log (from dmesg):
    [ 8227.059704] ipython[6308]: segfault at 0 ip 00007f1f679c9849 sp 
00007fffce31e1b0 error 4 in libreadline.so.6.3[7f1f679b2000+40000]

Ipython session:
    In [1]: "[1]    6308 segmentation fault (core dumped)  ipython

version information:
    uname -sr:
        Linux 3.13.6-1-ARCH
    ipython --version
        1.2.1
    pacman -Qs readline
        local/readline 6.3-1
            GNU readline library