treewide: use blas and lapack

This makes packages use lapack and blas, which can wrap different
BLAS/LAPACK implementations.

treewide: cleanup from blas/lapack changes

A few issues in the original treewide:

- can’t assume blas64 is a bool
- unused commented code

pkgs/applications/science/math/cntk/default.nix

@@ -1,11 +1,12 @@
 { lib, stdenv, fetchgit, fetchFromGitHub, cmake
-, openblas, opencv3, libzip, boost, protobuf, openmpi
+, openblas, blas, lapack, opencv3, libzip, boost, protobuf, openmpi
 , onebitSGDSupport ? false
 , cudaSupport ? false, addOpenGLRunpath, cudatoolkit, nvidia_x11
 , cudnnSupport ? cudaSupport, cudnn
 }:
 
 assert cudnnSupport -> cudaSupport;
+assert blas.implementation == "openblas" && lapack.implementation == "openblas";
 
 let
   # Old specific version required for CNTK.