Ensure unpickles equally on callbacks

Closes #136

See merge request inducer/loopy!267

Reenable pypy and binary-build CI

See merge request inducer/loopy!266

No defaultdict for iname to tags

See merge request inducer/loopy!265

Merge branch 'add-local-strides-global-strides-and-var-name-to-local-mem-access-stats' into 'master'

Now counting lid strides, gid strides, and variable name in LocalMemAccessCounter. Updated tests accordingly.

See merge request !263

Fix various issues with dependency cycles

See merge request !264

draw_dependencies_as_unicode_arrows: Fix (never-ending) drawing of downward arrows, indicating cyclic deps

now counting lid_strides, gid_strides, and variable name in LocalMemAccessCounter; updated tests accordingly

use iname_to_tags instead of iname_to_tag

See merge request inducer/loopy!258

Allowing multiple tags for inames

See merge request !249