Use mpfr_const_log2

[devmotion]

This PR changes the implementation of logtwo such that they use mpfr_const_log2. The resulting definition for BigFloat is very similar to https://github.com/JuliaLang/julia/blob/f5d944c453c2cbfee1a1765f0d6a5fc38597494e/base/mpfr.jl#L620-L624 but additionally it is possible to specify precision and rounding mode:

julia> @macroexpand Base.@irrational logtwo 0.6931471805599453094 log2
quote
    #= irrationals.jl:187 =#
    const logtwo = Base.Irrational{:logtwo}()
    #= irrationals.jl:188 =#
    begin
        #= irrationals.jl:173 =#
        function (Base.Base).BigFloat(::Base.Irrational{:logtwo}, var"#97#r"::(Base.MPFR).MPFRRoundingMode = (Base.MPFR).ROUNDING_MODE[]; precision = precision(Base.BigFloat))
            #= irrationals.jl:173 =#
            #= irrationals.jl:174 =#
            var"#95#c" = Base.BigFloat(; precision = precision)
            #= irrationals.jl:175 =#
            ccall(("mpfr_const_log2", :libmpfr), Base.Cint, (Base.Ref{Base.BigFloat}, (Base.MPFR).MPFRRoundingMode), var"#95#c", var"#97#r")
            #= irrationals.jl:177 =#
            return var"#95#c"
        end
    end
    #= irrationals.jl:189 =#
    (Base.Base).Float64(::Base.Irrational{:logtwo}) = begin
            #= irrationals.jl:189 =#
            0.6931471805599453
        end
    #= irrationals.jl:190 =#
    (Base.Base).Float32(::Base.Irrational{:logtwo}) = begin
            #= irrationals.jl:190 =#
            0.6931472f0
        end
    #= irrationals.jl:191 =#
    if Base.big(logtwo) isa Base.BigFloat
        nothing
    else
        Base.throw(Base.AssertionError("big(\$(Expr(:escape, :logtwo))) isa BigFloat"))
    end
    #= irrationals.jl:192 =#
    if Base.Float64(logtwo) == Base.Float64(Base.big(logtwo))
        nothing
    else
        Base.throw(Base.AssertionError("Float64(\$(Expr(:escape, :logtwo))) == Float64(big(\$(Expr(:escape, :logtwo))))"))
    end
    #= irrationals.jl:193 =#
    if Base.Float32(logtwo) == Base.Float32(Base.big(logtwo))
        nothing
    else
        Base.throw(Base.AssertionError("Float32(\$(Expr(:escape, :logtwo))) == Float32(big(\$(Expr(:escape, :logtwo))))"))
    end
end

[coveralls]

Pull Request Test Coverage Report for Build 1333223844

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• Overall coverage remained the same at 100.0%

---

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Change from base Build 1333199438:	0.0%
Covered Lines:	0
Relevant Lines:	0

---

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[codecov]

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[devmotion]

Bump 🙂