A more robust error bound for the determinant. Remove Float16 from linalg tests. Add fallback condition number method.
make fallback hypot() behave the same for inf and nan as standard implementations
fix #6074, macroexpander bug in `let`
fix show() of 1-argument calls to binary operators

we were doing this:

```
julia> :((%)(x))
:(x)
```
Merge pull request #5902 from JuliaLang/anj/detbound

A more robust error bound for the determinant.
add missing root
Merge pull request #6085 from carnaval/missingroot

add missing root