Auto merge of rust-lang#36940 - eulerdisk:incr_test_for_hash_trait, r=michaelwoerister

Test Case for Incr. Comp. Hash for traits rust-lang#36681.

Fixes rust-lang#36681
Part of rust-lang#36350

Currently, the following tests fail:

Unsafe modifier
Extern modifier
Extern c to rust-intrinsic
Trait unsafety
Change type of method parameter (&i32 => &mut i32)
Mode of self parameter

r? @michaelwoerister

Author: bors