I'll try to exlpain why. Calling conventions influence the prolog and epilog code generated by the compiler for each function. When calling a cdecl function, the caller is responsible for cleaning up the stack, say, the calling function pops the parameters passed to the called function. That means that only cdecl functions can do varargs. Since libxml2 contains one function or three with varargs, we cannot change the calling convention and, unfortunately, the naming decoration rule is bound to the calling convention.
Chances are good it can do so.
Ideally, you would use the source of libxml2 and try to generate the libxml2.DLL with Borland's compiler. That would be the best thing.