We have had several support cases with very non-obvious linking errors due to someone building the mongoclient library with its default cdecl calling convention, but then attempting to use it in a project with a different default calling convention, which is doomed to failure:

http://msdn.microsoft.com/en-us/library/46t77ak2(v=vs.110).aspx

We should provide a build system switch for the top level SConstruct to control what the default calling convention should be.

Note that this only affects 32 bit windows: 64 bit windows has only one calling convention.