proposal to add missing IEEE-754 functions

[everythingfunctional]

This proposes to add all of the missing functions from IEEE-754 Table 9.1.

Note: I did not add exp2 or exp10 as they are expressible as 2**x and 10**x already, but I would be willing to add them if there are some who believe there is reason to do so. Ditto for pow and pown, but I believe there is even less chance of reason to add them since x**y and x**n are exactly the same.

Fix #222

[everythingfunctional]

Note to those interested, IEEE-754 2019 can be found here.