Add absolute issue URL

Author: princejwesley

lib/repl.js

@@ -538,7 +538,7 @@ function REPLServer(prompt,
         cmd = `(${cmd})`;
         self.wrappedCmd = true;
       } else {
-        // Mitigate vm #548 issue
+        // Mitigate https://github.com/nodejs/node/issues/548
         cmd = cmd.replace(/^\s*function\s+([^(]+)/,
                   (_, name) => `var ${name} = function ${name}`);
       }

test/parallel/test-repl.js

@@ -328,7 +328,7 @@ function error_test() {
     // or block comment. https://github.com/nodejs/node/issues/3611
     { client: client_unix, send: 'a = 3.5e',
       expect: /^SyntaxError: Invalid or unexpected token/ },
-    // Mitigate #548 issue
+    // Mitigate https://github.com/nodejs/node/issues/548
     { client: client_unix, send: 'function name(){ return "node"; };name()',
       expect: "'node'\n" + prompt_unix },
     { client: client_unix, send: 'function name(){ return "nodejs"; };name()',