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 nested21;

extern(C) int printf(char*, ...);

void main() {
    int i = 42;
    int foo() { return i; }
    int bar() {
        int j = 47;
        int baz() { return j; }
        return foo() + baz();
    }
    auto result = bar();
    printf("%d\n", result);
    assert(result == 42 + 47);
}