Rollup merge of rust-lang#37610 - oldmanmike:unary-and-binary-tests, r=michaelwoerister

Add unary and binary tests for incr-comp

This is my draft of tests for unary and binary expressions as desired by rust-lang#37520 for use in the test suite for hashes in incremental compilation. Feedback would be wonderful, if there's any changes I need to make I would appreciate the code review.

?r @michaelwoerister

Author: steveklabnik