Implement all functions in #6148 except for 'pow' functions

Pretty much what the title says #6148 suggested adding several functions to Julia based on the IEEE-754 standard. All were possible to write with very brief, simple code. I didn't implement the `pow` functions, both because Julia provides exponentiation as an operator (rather than a function) and because some functionality will require #2976 to be completed first.
this is going backwards, you don't want this included here - should put this back to 5599b8

submodules are annoying like this - next time you see a weird diff in a submodule, try doing `git submodule update` and it should go away