Question: Suppose I have built a lot of dlls from a certain revision of the svn repository. (It might by any revisioning system)

I am able to create a resource file containing an entry that denotes the revision number.

Can I link that resource file into the dll's I have already built? Some sort of `editbin` or the like?

Answer: 
You can write a small program to do this, using the UpdateResource function in Windows NT:
<http://msdn.microsoft.com/en-us/library/ms648049(v=VS.85).aspx>
The resource compiler uses the C pre-processor. You can simply use a #define in a header file you #include in your .rc file. Or use the /D command line option for rc.exe. You can use the macro symbol in your resource definition.