Using D libs in C

[Dainius (GreatEmerald)]

All right, I solved that part of the problem by creating a linked
list. However, getting the string out of D is still problematic,
namely because toStringz() gives me an immutable char*, and I don't
seem to be able to pass those, since I can't assign those to immutable
variables outside their constructors. Also, if I use this:
//D:
void GetString()
{
    ReceiveString(toStringz(StringD));
}

//C:
extern(C) void ReceiveString(char* String)
{
    StringC = String;
}

DMD gives me "Error: undefined identifier ReceiveString" for some reason.