allow null filename to new_from_file and set_from_file, as documented in C API ref
allow null filename to new_from_file and set_from_file, as documented in C API ref

svn path=/trunk/; revision=952

potyl/perl-Gtk2,potyl/perl-Gtk2,cpanxaoc/perl-Gtk2,cpanxaoc/perl-Gtk2,potyl/perl-Gtk2,cpanxaoc/perl-Gtk2