* not for cmake build on windows

In Windows, the option WITH_PLUGINS is set to OFF, but in src/win32_config.h you can find #define WITH_PLUGINS 1.
This cause link errors when you link against librdkafka. So you have to manually set #define WITH_PLUGINS 0 for the cmake build to work properly.

* Add new preprocessor flag to avoid redefining macros defined by cmake

* Transform from CMake options to C preprocessor flags

* Add rddl.c on windows to avoid linker failures due to undefined rd_dl_open

* New CMake option to avoid win32 hand crafted config

* Add sources to rdkafka_cpp on Windows to make it compile.

* Add crypt32 static link dependency as stated on openssl notes on building under Windows.
"If you link with static OpenSSL libraries then you're expected to
 additionally link your application with WS2_32.LIB, GDI32.LIB,
 ADVAPI32.LIB, CRYPT32.LIB and USER32.LIB."
This maybe a feature request for CMake's FindOpenSSL.cmake module on Windows

* Make examples compile on Windows with CMake

* Make test compile on Windows with CMake

* Add export macros for shared builds on cmake

* Update README.md

Remove useless comment