Because .dbc is not a well used extension/file you will probably have to create your own.
If you know how the file is structured and whether its ascii or binary you could make a few functions yourself to create and edit the files.
The same thing you need to create and edit any other type of file. What is wrong with file streams? I don't believe that the C++ language provides any specific library specifically for dbc files. A file is a file. I'm confused by the question. Are you looking for an open source project or library that makes editing and parsing the files easier? Did you search the MSDN for information on that?