More 0.3.21 release prep

Bump version number in Windows installer file
Update READMEs.

doc/README

@@ -0,0 +1,30 @@
+Bitcoin 0.3.21 BETA
+
+Copyright (c) 2009-2011 Bitcoin Developers
+Distributed under the MIT/X11 software license, see the accompanying
+file license.txt or http://www.opensource.org/licenses/mit-license.php.
+This product includes software developed by the OpenSSL Project for use in
+the OpenSSL Toolkit (http://www.openssl.org/).  This product includes
+cryptographic software written by Eric Young (eay@cryptsoft.com).
+
+
+Intro
+-----
+Bitcoin is a free open source peer-to-peer electronic cash system that is
+completely decentralized, without the need for a central server or trusted
+parties.  Users hold the crypto keys to their own money and transact directly
+with each other, with the help of a P2P network to check for double-spending.
+
+
+Setup
+-----
+Unpack the files into a directory and run:
+ bin/32/bitcoin (GUI, 32-bit)
+ bin/32/bitcoind (headless, 32-bit)
+ bin/64/bitcoin (GUI, 64-bit)
+ bin/64/bitcoind (headless, 64-bit)
+
+See the documentation at the bitcoin wiki:
+  https://en.bitcoin.it/wiki/Main_Page
+
+... for help and more information.