[js] Implement stuff needed to get test 19 to pass again.

Implement nqp::rename, nqp::copy.
Make nqp::unlink fail quietly when it's target doesn't exit.

Author: pmurias

src/vm/js/Operations.nqp

@@ -458,6 +458,8 @@ class QAST::OperationsJS {
     add_simple_op('isttyfh', $T_INT, [$T_OBJ]);
     add_simple_op('setinputlinesep', $T_OBJ, [$T_OBJ, $T_STR], :sideffects);
     add_simple_op('setinputlineseps', $T_OBJ, [$T_OBJ, $T_OBJ], :sideffects);
+    add_simple_op('copy', $T_VOID, [$T_STR, $T_STR], :sideffects);
+    add_simple_op('rename', $T_VOID, [$T_STR, $T_STR], :sideffects);
 
     add_simple_op('bootarray', $T_OBJ, []);
 

src/vm/js/nqp-runtime/io.js

@@ -321,7 +321,13 @@ op.sayfh = function(fh, content) {
 };
 
 op.unlink = function(filename) {
-  fs.unlinkSync(filename);
+  try {
+    fs.unlinkSync(filename);
+  } catch (e) {
+    if (e.code !== 'ENOENT') {
+      throw e;
+    }
+  }
 };
 
 op.link = function(srcpath, dstpath) {
@@ -461,3 +467,11 @@ op.sleep = function(seconds) {
   sleep.usleep(Math.floor(seconds * 1000000));
   return seconds;
 };
+
+op.copy = function(source, target) {
+  fs.writeFileSync(target, fs.readFileSync(source));
+};
+
+op.rename = function(oldPath, newPath) {
+  fs.renameSync(oldPath, newPath);
+};