incr.comp.: Add missing match branch in HashStable impl for ty::RegionKind.
incr.comp.: Add missing match branch in HashStable impl for ty::RegionKind.

aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,GBGamer/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,graydon/rust