- Make `extern fn()` assignable to any closure type, rather than
a subtype.
- Remove unused int_ty_set and float_ty_set
- Refactor variable unification and make it more DRY
- Do fn sub/lub/glb on the level of fn_sig
- Rename infer::to_str::ToStr to infer::to_str::InferStr
- Capitalize names of various types
- Correct hashing of FnMeta
- Convert various records-of-fns into structs-of-fns. This is both
eliminating use of deprecated features and more forwards compatible
with fn reform.
r=pcwalton
New style is allow(foo), warn(foo), deny(foo) and forbid(foo),
mirrored by -A foo, -W foo, -D foo and -F foo on command line.
These replace -W no-foo, -W foo, -W err-foo, respectively.
Forbid is new, and means "deny, and you can't override it".
Under this scheme when parsing foo.rc the parser will also look for
foo.rs to fill in the crate-level module, and when evaluating a
directory module directive it will look for a .rs file with the
same name as the directory.
