tidy macro just a bit
revive old commented-out test cases as ignored test cases for hygiene
comments only
enrich and rename crate_idents test case
add unit test for match var hygiene
remove unneeded visit_ty methods
remove unneccessary pubs, shorten names
remove misleading and unnecessary underscores
don't expand subexprs of for loop, just re-expand whole thing.
added compile-fail test for 15167
make macros hygienic