Visual Studio 2012 and C++ Compatibility

Upgrade project and solution files to Visual Studio 2012
Changes to headers to reduce conflicts with any C++ code that might be using CZMQ
Generate debug info for testing
Rearrange build process to be friendlier in Visual Studio
Resource file will populate version information in the DLL
Modify exporting of zctx_interrupted (Visual Studio doesn't seem to like exporting extern volatile data from shared libraries)
(This is all in preparation for my upcoming pull request that will port Zyre to C++11)
((First time contributor!))