Initial commit: up to and including data exchange functionality

This initial commit for the PyDTLS package includes the following functionality:

    * DTLS cookie exchange, using secure hmac cookies
    * A platform-independent routing UDP demultiplexer
    * SSL handshaking over UDP using the DTLS protocol
    * Datagram exchange using the DTLS protocol
    * SSL shutdown over UDP

The package is structured as follows:

    * dtls:               top-level package
    * dtls.demux:         demultiplexer package; automatically loads a
                          demultiplexer appropriate for the currently executing
                          platform
    * dtls.demux.router:  a routing demux for platforms whose network stacks
                          cannot assign incoming UDP packets to sockets based
                          on the sockets' connection information
    * dtls.demux.osnet:   a demux that uses the operating system's UDP packet
                          routing functionality
    * dtls.err:           package-wide error handling and error definitions
    * dtls.sslconnection: a client and server-side connection class for
                          UDP network connections secured with the DTLS protocol
    * dtls.openssl:       a ctypes-based wrapper for the OpenSSL library
    * dtls.test:          test scripts, utilities, and unit tests

The following binaries are provided:

    * libeay32.dll: cryptographic portion of the OpenSSL library
    * ssleay32.dll: protocol portion of the OpenSSL library (depends on former)
    * cygcrypto-1.0.0.dll: as libeay32.dll, but with debugging symbols
    * cygssl-1.0.0.dll: as ssleay32.dll, but with debugging symbols

All binaries have been built with the MinGW tool chain, targeted for msvcr90.
The unstripped dll's can be debugged on Windows with gdb. Cygwin is not used.

dtls/__init__.py

@@ -0,0 +1,11 @@
+# PyDTLS: datagram TLS for Python. Written by Ray Brown.
+"""PyDTLS package
+
+This package exports OpenSSL's DTLS support to Python. Importing it will add
+the constant PROTOCOL_DTLSv1 to the Python standard library's ssl module.
+Passing a datagram socket to that module's wrap_socket function (or
+instantiating its SSLSocket class with a datagram socket) will activate this
+module's DTLS implementation for the returned SSLSocket instance.
+
+wrap_socket's parameters and their semantics have been maintained.
+"""