Add web worker support. Load the whole library in a web worker

and make the high-level API accessible from an asynchronous proxy.
Entropy is seeded to worker on each generateKeyPair() call.
Allow serialization of packets and custom types for messaging API.

src/type/keyid.js

@@ -65,3 +65,9 @@ Keyid.prototype.isNull = function() {
 module.exports.mapToHex = function (keyId) {
   return keyId.toHex();
 };
+
+module.exports.fromClone = function (clone) {
+  var keyid = new Keyid();
+  keyid.bytes = clone.bytes;
+  return keyid;
+};

src/type/mpi.js

@@ -100,3 +100,12 @@ MPI.prototype.toBigInteger = function () {
 MPI.prototype.fromBigInteger = function (bn) {
   this.data = bn.clone();
 };
+
+module.exports.fromClone = function (clone) {
+  clone.data.copyTo = BigInteger.prototype.copyTo;
+  var bn = new BigInteger();
+  clone.data.copyTo(bn);
+  var mpi = new MPI();
+  mpi.data = bn;
+  return mpi;
+};

src/type/s2k.js

@@ -178,3 +178,12 @@ S2K.prototype.produce_key = function (passphrase, numBytes) {
 
   return result.substr(0, numBytes);
 };
+
+module.exports.fromClone = function (clone) {
+  var s2k = new S2K();
+  this.algorithm = clone.algorithm;
+  this.type = clone.type;
+  this.c = clone.c;
+  this.salt = clone.salt;
+  return s2k;
+};