0.25.2

Added

• Flattening/unflattening as the final operation in an entry point no
  longer forces a copy.

• The opencl backend no longer always fails on platforms that do
  not support 64-bit integer atomics, although it will still fail if
  the program needs them.

• Various performance improvements to the compiler itself;
  particularly the frontend. It should be moderately faster.

Fixed

• Code generation for f16 literals in CUDA backend (#1979).

• Branches that return arrays differing in sign of their stride
  (#1984).