[Dune] Problems with linking an external library

[Christian Engwer]

Dear Andrea,

> extern "C"{
> #include "ldl.h"
> }

this is not a work-around, but the correct way to handle legacy
C-headers.

C++ allows many functions with the name name, but different
parameters, thus the C++ compiler automatically created new names,
wwhich include the parameters, i.e. mangled names. YOur problem was
that the lib included the plain C-names, but the program references
the mangled name.

Ciao
Christian