Array: Handle no-queue in __str__, __repr__ more gracefully

Add note to install docs about mixing conda forge and pypi installations

Array.__repr__: Make CL arrays visually distinguishable from numpy arrays

Fix doc reference to enqueue_copy in subst.rst

Don't use enqueue_fill_buffer for large arrays on NVIDIA

Co-authored-by: Andreas Klöckner <inform@tiker.net>

Fix get_sub_group_info version requirement

This reverts commit a60b4ed1.

This reverts commit ec5ca5d5.

Handle empty reductions (Closes gh-330)

Migrate in immediate allocator

See merge request !128

Fix get_pyopencl_fixture_arg_values to correctly enumerate over all devices

pipe: make it compile with OpenCL < 2

Reinstate Gitlab Titan V CI

See merge request !127

Aksetup fixes