Native win32 build instructions using Microsoft Visual Studio 2013 (MSVC).

Requirements:
 * zlib is installed automatically from NuGet,
   but probably requires the NuGet VS extension.
 * OpenSSL-win32 must be installed in C:\OpenSSL-win32.
   Download and install the latest v1.0.2 non-light package from:
   https://slproweb.com/products/Win32OpenSSL.html
   (This would be using NuGet too but the current
    OpenSSL packages are outdated and with broken
	dependencies, so no luck)


The Visual Studio solution file for librdkafka resides in win32/librdkafka.sln

Artifacts:
 - C library
 - C++ library
 - rdkafka_example
 - tests

 Missing:
  - remaining tools (rdkafka_performance, etc)
  - SASL support (no official Cyrus libsasl2 DLLs available)
  - LZ4 support