Fixed several cases of unsafe use of get_all_args for optional args.

Rev: src/builtin_functions.c:1.704
Rev: src/cpp.c:1.178
Rev: src/modules/Gettext/gettext.c:1.28
Rev: src/modules/Image/font.c:1.92
Rev: src/modules/_Roxen/roxen.c:1.56
Rev: src/modules/files/socket.c:1.112
Rev: src/modules/files/udp.c:1.84
Rev: src/post_modules/GTK2/source/gnomecanvas.pre:1.8
Rev: src/post_modules/GTK2/source/gtksourceiter.pre:1.7
Rev: src/post_modules/GTK2/source/gtktextiter.pre:1.14