Release 0.3.2.

[cfallin]

Includes:

• resolve_aliases: resolve every terminator use, not only branch args. #22: completeness fix for resolve_aliases pass.
• Backend: avoid recursion; use explicit stack with iteration instead. #23: scalability improvement in backend for very large functions (which result in very deeply-nested Wasm structured control flow trees).
• Make passes::empty_blocks::run public. #24: make the empty-blocks pass public.

[cfallin]

(Queueing this up along with the above three PRs; will not merge until those are merged.)