Remove unused `kind` field in ALoc
Remove unused `kind` field in ALoc

Summary:
This improves memory usage when abstract locations is turned on, without affecting time.

See the comments for an explanation. One hesitation I had about making this change was whether polymorphic compare (which we, unfortunately, use extensively) would tolerate comparing two values of different sizes. It turns out that it handles this case just fine!

Reviewed By: jbrown215

Differential Revision: D16466186

fbshipit-source-id: caec3c3fceaa55996132a68bf949d922e38b6a19

nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow