Grabbag of fixes for 0.7 (#64)

Fix uses of now-lazy adjoint (#50)

Use MKL for FFTs if Julia's BLAS is MKL (#42)

Use the FFTW binaries from fftw-builder (#30)

* Temporarily mark the 2D brfft inference test as broken

* Also mark 2D plan_bfft inference test as broken

* Mark more inference tests as broken

* Replace uses of ANY

* Fully switch to where syntax

Wrap everything in a version check

Elliot's fix

* Remove DSP functions (to be rehomed)

* Remove DSP doc file from the doc build

* Copy necessary DCT tests to runtests.jl

* Ensure DCT functions are called from the package, not Base