improve compression of undefined, NaN & Infinitiy (#1748)

improve compression of undefined, NaN & Infinitiy (#1748)

- migrate transformation logic from `OutputStream` to `Compressor`
- always turn `undefined` into `void 0` (unless `unsafe`)
- always keep `NaN` except when avoiding local variable redefinition
- introduce `keep_infinity` to suppress `1/0` transform, except when avoiding local variable redefinition

supersedes #1723
fixes #1730