Provide more "inline" operators such as copysign, isfinite, etc...

[eschnett]

Certain math functions such as copysign can be implemented efficiently with bitwise operations. It would be convenient to have these available:

• copysign
• isfinite
• isinf
• isnan
• isnormal
• signbit

I find the non-standard flipsign function https://docs.julialang.org/en/v1/base/math/#Base.flipsign convenient, e.g. to implement upwind finite differencing stencils. It can be defined as

flipsign(x, y) = copysign(1, y) * x

but can be implemented more efficiently as

flipsign(x, y) = x ^ (y & SIGNMASK)

[gquintin]

This issue is more general than #32, so I am closing #32.

[gquintin]

I put the text of issue #93 into your orginal request to have it all here.