always define convert_from_gpgme_sig_notation_flags_t, just return a bogus value (NoFlags) if there is no notation flag support. this allows gpgme++ to build on systems without this support in their libgpgme. i suppose that's why there is a configure check for it in the first place ;) ran into this at t.'s place tonight setting up kde4 for the book project.

svn path=/trunk/KDE/kdepimlibs/; revision=693517