added additional argument to _cairo.so after getting segmentation faults

When testing fieldpapers on Ubuntu 12.04 64bit, I consistently got a Segmentation Fault during use of cairo shared object from decoder/svgutils.  I found the fix right in the doc string for the function which included a link to the code example that was used for interfacing with cairo through ctypes.

I added the missing argument mapping in and everything is working fine on precise64.

http://cairographics.org/freetypepython/

Any idea why these argument may have been removed earlier?  In any case, not more seg fault.