fix binaryFun

Old log:#2720
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: [Issue 13253 - use more scoped imports in phobos](https://issues.dlang.org/show_bug.cgi?id=13253)
Even if it is private those functions still need documentation so that they can be easier replaced with public alternatives later once inter-dependency hell is figured out.