librustc: Replace all uses of `fn()` with `&fn()`. rs=defun
libsyntax: Stop parsing bare functions in preparation for switching them over
test: Remove newtype enums from the test suite. rs=deenum
libstd: Remove all newtype enums from std and core.
librustc: Remove newtype enums from librustc
libsyntax: Remove newtype enums from libsyntax. rs=deenum
doc: Remove documentation on newtype enums.
libsyntax: Stop parsing newtype enums
test: Fix tests. rs=tests