Add hyperbolic trig functions

[rtavenner]

Suggestion: Provide hyperbolic trig functions (sinh, cosh, tanh, asinh, acosh, atanh) in Basics.
All of these are already javascript functions (Math.cosh, Math.sinh, etc.), so this should be easy to implement.

Current workaround:

cosh : Float -> Float
cosh x = (e^x + e^ -x) / 2
sinh : Float -> Float
sinh x = (e^x - e^ -x) / 2
tanh x : Float -> Float
tanh x = sinh x / cosh x
asinh : Float -> Float
asinh x = logBase e (x + sqrt (1 + x^2))
acosh : Float -> Float
acosh x = logBase e (x + sqrt (x^2 - 1))
atanh : Float -> Float
atanh x = (logBase e ((1 + x) / (1 - x))) / 2

(I got these formulas from Wolfram Mathworld.)

I use these functions a lot! In my own code, I have manually defined cosh and sinh 5 times, acosh 3 times, and asinh twice.

Note: This suggestion probably belongs in the meta-issue "Math and Numbers" (#721).