fix issue links

Author: stevengj

NEWS.md

@@ -445,7 +445,7 @@
 
 * Initial public release.
 
-<!--- generated by julia/doc/NEWS-update.jl: -->
+<!--- generated by script similar to julia/doc/NEWS-update.jl: -->
 [#12]: https://github.com/stevengj/nlopt/issues/12
 [#13]: https://github.com/stevengj/nlopt/issues/13
 [#21]: https://github.com/stevengj/nlopt/issues/21
@@ -462,12 +462,15 @@
 [#257]: https://github.com/stevengj/nlopt/issues/257
 [#258]: https://github.com/stevengj/nlopt/issues/258
 [#261]: https://github.com/stevengj/nlopt/issues/261
+[#268]: https://github.com/stevengj/nlopt/issues/268
 [#278]: https://github.com/stevengj/nlopt/issues/278
 [#303]: https://github.com/stevengj/nlopt/issues/303
 [#308]: https://github.com/stevengj/nlopt/issues/308
 [#314]: https://github.com/stevengj/nlopt/issues/314
 [#317]: https://github.com/stevengj/nlopt/issues/317
 [#319]: https://github.com/stevengj/nlopt/issues/319
-[#319]: https://github.com/stevengj/nlopt/issues/355
-[#319]: https://github.com/stevengj/nlopt/issues/361
-[#319]: https://github.com/stevengj/nlopt/issues/365
+[#355]: https://github.com/stevengj/nlopt/issues/355
+[#361]: https://github.com/stevengj/nlopt/issues/361
+[#365]: https://github.com/stevengj/nlopt/issues/365
+[#409]: https://github.com/stevengj/nlopt/issues/409
+[#420]: https://github.com/stevengj/nlopt/issues/420