new_mark -> apply_mark, new_rename -> apply_rename
comments only
use PatIdentRenamer for match bindings
comments & test cases for IdentRenamers
hygiene for item fn args

also, introduce fn_decl_arg_bindings abstraction
new expand_and_rename abstraction
make any_pat! and u64_from_be_bytes_bench_impl! macros hygienic
comments only
added test cases for closure arg hygiene
implement hygiene for ExprFnBlock and ExprProc
DONT LET THIS COMMIT GO UPSTREAM
added test for method arg hygiene
implement hygiene for method args