Remove the FFTW bindings from Base

[ararslan]

Ready to merge!

This PR completely removes FFTW from Base. The bindings will instead be available in the FFTW.jl package in the JuliaMath organization. I'm still working on the package, but in the meantime I figured I'd put this up here to give folks a preview of what's to come.

• DFT framework -> AbstractFFTs.jl
• FFTW bindings -> FFTW.jl
• DSP functions -> DSP.jl

Fixes #18389

[ararslan]

@jlbuild !nuke

Pkg.clone("https://github.com/JuliaMath/FFTW.jl.git")
Pkg.checkout("FFTW", "master")
Pkg.build("FFTW")
Pkg.test("FFTW")

[jlbuild]

Status of 65bb63f builds:

Builder Name	Nuke	Build	Download	Code Output
linux32	COMPLETE	COMPLETE	Download	COMPLETE
linux64	COMPLETE	COMPLETE	Download	ERRORED
linuxaarch64	COMPLETE	COMPLETE	Download	ERRORED
linuxarmv7l	COMPLETE	COMPLETE	Download	COMPLETE
linuxppc64le	COMPLETE	COMPLETE	Download	COMPLETE
osx64	COMPLETE	COMPLETE	Download	PENDING
win32	COMPLETE	ERRORED	N/A	N/A
win64	COMPLETE	ERRORED	N/A	N/A

[ararslan]

This is getting really close. This PR, AbstractFFTs, and FFTW are ready to go, I just need to finish up the DSP package.

[ararslan]

The packages that inherited these functions are ready now, so this is good to go!

[ararslan]

Four hours in the CI queue after a rebase, but now it's good to go.

[StefanKarpinski]

do it

[ararslan]

i did it

[StefanKarpinski]

Probably should have tried this before we merged this, but I'm seeing this:

julia> fft(rand(10))
ERROR: UndefVarError: pkg not defined
Stacktrace:
 [1] #fft#6(::Array{Any,1}, ::Function, ::Array{Float64,1}, ::Vararg{Array{Float64,1},N} where N) at ./deprecated.jl:1448
 [2] fft(::Array{Float64,1}, ::Vararg{Array{Float64,1},N} where N) at ./deprecated.jl:1448

[JeffBezanson]

Ah, string interpolation strikes again

[ararslan]

Ah crap. Will fix.

[ararslan]

Fix in #22391

[martinholters]

Something is still not quite as it should here (or am I missing something?), but the problem might be with DSP.jl?

   _       _ _(_)_     |  A fresh approach to technical computing
  (_)     | (_) (_)    |  Documentation: https://docs.julialang.org
   _ _   _| |_  __ _   |  Type "?help" for help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 0.7.0-DEV.1776 (2017-09-14 03:47 UTC)
 _/ |\__'_|_|_|\__'_|  |  Commit deceb3be66* (7 days old master)
|__/                   |  x86_64-linux-gnu

julia> Pkg.status("DSP")
 - DSP                           0.3.2

julia> using DSP

julia> xcorr([1, 2], [3, 4])
ERROR: Base.DSP.xcorr has been moved to the package DSP.jl.
Run `Pkg.add("DSP")` to install it, restart Julia,
and then run `using DSP` to load it.
Stacktrace:
 [1] error(::Function, ::String, ::String, ::String, ::String, ::String, ::String, ::String, ::String, ::String) at ./error.jl:44
 [2] #xcorr#6(::Array{Any,1}, ::Function, ::Array{Int64,1}, ::Vararg{Array{Int64,1},N} where N) at ./deprecated.jl:126
 [3] xcorr(::Array{Int64,1}, ::Vararg{Array{Int64,1},N} where N) at ./deprecated.jl:126

OTOH:

julia> using DSP: xcorr

julia> xcorr([1, 2], [3, 4])
3-element Array{Int64,1}:
  4
 11
  6

Edit: Fixed in DSP.jl.