fix binaryFun

1. Make binaryFun correct for integer comparison.
2. Remove import of half of phobos for 98% 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)

I don't see how lines 243-247 are relevant to my question – whether `binaryFun` aliases to a given symbol or to a semantically equivalent one doesn't matter for its semantics. Regarding `safeOp`: This means that after your change, _more_ code yields the expected result, right? That is, this is not a potentially breaking change? (Well, if somebody relied on overflow, it probably still is…)