Deal with moval of Base.LinAlg to LinearAlgebra stdlib package

Should be able to simplify this once Compat has JuliaLang/Compat.jl#463
in.

src/definitions.jl

@@ -1,8 +1,14 @@
 # This file was formerly a part of Julia. License is MIT: https://julialang.org/license
 
-using Base.LinAlg: BlasReal
+if VERSION ≥ v"0.7.0-DEV.3449"
+    using LinearAlgebra: BlasReal, UniformScaling, I, scale!
+    import LinearAlgebra: A_mul_B!, A_ldiv_B!
+else
+    using Base.LinAlg: BlasReal
+    import Base: A_mul_B!, A_ldiv_B!
+end
 import Base: show, summary, size, ndims, length, eltype,
-             *, A_mul_B!, inv, \, A_ldiv_B!
+             *, inv, \
 
 # DFT plan where the inputs are an array of eltype T
 abstract type Plan{T} end