Don't print the entire declaration of the alliassee when `->toChars()` is called on an `AliasDeclaration`; just printing the name will do. This fixes #305, which otherwise tries to generate {{{ class E { void A() { alias /* recurse into E->toCBuffer() */ m; } } }}} by way of an infinite recursion (causing a segfault when the stack runs out).

module enum3;

enum GE : ushort
{
    A,B,C
}

void main()
{
    GE e = GE.B;
    size_t s = GE.sizeof;
    assert(e == 1);
    assert(e.sizeof == s);
    assert(s == 2);
}