middle: ty: remove dead code
middle: typeck: check: remove dead code
middle: typeck: infer: combine: remove dead code
middle: typeck: infer: lub: remove dead code
middle: typeck: infer: remove dead code
middle: typeck: infer: resolve: remove dead code
middle: typeck: remove dead code
middle: typeck: rscope: remove dead code
util: common: remove dead code
util: ppaux: remove dead code
metadata: common: renumber tags