Allow exact arguments to numeric functions
Allow exact arguments to numeric functions

`log1p`, `expm1`, and `hypot` were all defined to be the `fl*` versions
of those functions, which don't allow non-flonum arguments. New version
uses the flonum version if it can, otherwise falls back to the direct
formula.

Fixes #73.

jackfirth/herbie,jackfirth/herbie,jackfirth/herbie,jackfirth/herbie,jackfirth/herbie,jackfirth/herbie