Fixed method&attribute add bugs

Seems like nobody noticed this--when adding methods
or attributes under certain conditions (I've seen
this only under Win32), you'd get garbage characters
in the dialogs.

Turns out we were doing something bad, and it's
all Bill's fault. :{)

Returning a temporary string's c_str() for
a const char* returning-function is *not* a good
idea.

I'll probably make a new release soon, because
I consider this to be a critical bug.