Revert "Process symlinked shared library as .node"

This reverts commit 7e0bf7d57d.

It's possible to make GYP generate an XCode project that produces a .node file,
hence this commit is no longer needed.

lib/module.js

@@ -469,11 +469,11 @@ Module._extensions['.json'] = function(module, filename) {
 };
 
 
-//Native extension for .node and OS-specific equivalents
+//Native extension for .node
 Module._extensions['.node'] = function(module, filename) {
   process.dlopen(filename, module.exports);
 };
-Module._extensions['.dylib'] = Module._extensions['.node'];
+
 
 // bootstrap main module.
 Module.runMain = function() {