Having these as class statics visible to header consumers has effects when DLL visibility is in play, in particular the "two variables on one line" thing seems to be baffling MSVC in some bizarre way:

C:\cygwin\home\andrew\Documents\10gen\dev\opt\include\mongo/bson/oid.h(118) : error C2487: 'ourMachineAndPid' : member of dll interface class may not
be declared with dll interface

These statics are private, so they should just be scoped to OID.cpp rather than to class OID.

We can either fix this in the server codebase and pick it up in the C++ driver repo, or, if not, the C++ driver codebase will make this change.