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).

[Environment]
DFLAGS=-I@RUNTIME_DIR@/import -L-L%@P%/../lib -defaultlib=@RUNTIME_AIO@ -debuglib=@RUNTIME_AIO@