Improve size annotation support in type checker.
Improve size annotation support in type checker.

HIPERFIT/futhark,diku-dk/futhark,diku-dk/futhark,HIPERFIT/futhark,HIPERFIT/futhark,diku-dk/futhark,mrakgr/futhark,mrakgr/futhark,ihc/futhark,diku-dk/futhark,diku-dk/futhark,ihc/futhark,CulpaBS/wbBach,ihc/futhark,mrakgr/futhark