fix binaryFun

1. Make binaryFun correct for integer comparison.
2. Remove import of half of phobos for 100% cases in phobos.

`sort`, `cmp`, `find`, `startsWith`,  `sum` and other algorithms would be compiled faster.

See also: #2701, [Issue 13253 - use more scoped imports in phobos](https://issues.dlang.org/show_bug.cgi?id=13253)

Actually you can skip unary here ;)

And if you add separate stage for indexing as "primary expression" that is used in unary you'd get even further ahead in what it deduces as simple expressions such as `-a < -b`.

Ultimately this gets us simplistic recursive descent parser, it's only a question of balance and taste to know where to stop.