Fix #198 and #199 by making CTFE on static struct initializers work. Renamed SymbolDeclaration to StaticStructInitDeclaration to make its usage clearer.

module structs7;

struct S
{
    int i;
    long l;
}

void main()
{
    S s = void;
    int i = s.i;
    long l = s.l;
}