SSL.Context.load_verify_locations

I have two problems with SSL.Context.load_verify_locations:

- OpenSSL regards each of the args cafile and capath as optional, but m2crypto requires
the cafile arg to be present (via an assertion).  Is there a reason for this?

- Since these are string args, SWIG requires that they be so, and doesn't allow None to be
passed in (for mapping to NULL in the C code).  A SWIG typemap to map from Py_None to NULL
for 'char *' args would do the trick (and, in fact, seems like the right thing for SWIG to
do in general).  Is there another way round this problem?

I can easily make these changes myself, but wanted to mail the list first and see if I
missed something.

Tom