PDF renderer draws strange artifacts on '%' character in 1.1.1

Hi there, 
The following code: 

``` python
from matplotlib import use
use("pdf")
import matplotlib.pyplot as plt
plt.title("Is there a bug?%%")
plt.savefig("test.pdf")
plt.close
```

..produces a PDF with strange arrow artiacts overlaying the '%' characters.

This i a regression since 1.1.0. 

Matplotlib version: 1.1.1
Backend: PDF
Arch: x86_64
Python: 2.6.2

Thanks,
Edward
