Restored Chebyshev.lean, and moved new files to a new folder, "ChebyshevReal"

Author: YuvalFilmus

Mathlib/Analysis/SpecialFunctions/Trigonometric/Chebyshev.lean

@@ -5,7 +5,7 @@ Authors: Johan Commelin
 -/
 import Mathlib.Data.Complex.Trigonometric
 import Mathlib.Data.Complex.Module
-import Mathlib.RingTheory.Polynomial.Chebyshev.Basic
+import Mathlib.RingTheory.Polynomial.Chebyshev
 
 /-!
 # Multiple angle formulas in terms of Chebyshev polynomials

…ngTheory/Polynomial/Chebyshev/Basic.lean …lib/RingTheory/Polynomial/Chebyshev.leanMathlib/RingTheory/Polynomial/Chebyshev/Basic.lean renamed to Mathlib/RingTheory/Polynomial/Chebyshev.lean Mathlib/RingTheory/Polynomial/Chebyshev/Basic.lean renamed to Mathlib/RingTheory/Polynomial/Chebyshev.lean

@@ -1,9 +1,9 @@
 /-
-Copyright (c) 2020 Johan Commelin. All rights reserved.
+Copyright (c) 2020 Yuval Filmus. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Yuval Filmus
 -/
-import Mathlib.RingTheory.Polynomial.Chebyshev.Basic
+import Mathlib.RingTheory.Polynomial.Chebyshev
 import Mathlib.Data.Real.Basic
 import Mathlib.Algebra.Polynomial.Roots
 import Mathlib.Analysis.SpecialFunctions.Trigonometric.Basic

…ingTheory/Polynomial/Chebyshev/Real.lean …eory/Polynomial/ChebyshevReal/Basic.leanMathlib/RingTheory/Polynomial/Chebyshev/Real.lean renamed to Mathlib/RingTheory/Polynomial/ChebyshevReal/Basic.lean Mathlib/RingTheory/Polynomial/Chebyshev/Real.lean renamed to Mathlib/RingTheory/Polynomial/ChebyshevReal/Basic.lean

@@ -1,9 +1,9 @@
 /-
-Copyright (c) 2020 Johan Commelin. All rights reserved.
+Copyright (c) 2020 Yuval Filmus. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Yuval Filmus
 -/
-import Mathlib.RingTheory.Polynomial.Chebyshev.Real
+import Mathlib.RingTheory.Polynomial.ChebyshevReal.Basic
 import Mathlib.LinearAlgebra.Lagrange
 import Mathlib.Topology.Algebra.Polynomial