Enable all the pedantic lints and fix warnings.
Notable items:
- `enum_glob_used` import types with a single character alias
- `doc_markdown`: add a whitelist that includes SegWit and OpenSSL
There is a range of different wordings used in the docs of constructor
type functions.
Change all to start with `Constructs a new` or `Constructs an empty`.
In functions that act like constructors there is a mixture of the usage
of `creates` and `constructs`.
Replace all occurrences of `creates` with `constructs` in the first line
of docs of constructor like functions.
Currently we feature gate code within the `impl_to_hex_from_lower_hex`
macro on "alloc" but `bitcoin` does not have the "alloc" feature so
this code is never built in. This can be seen by the lack of a
`to_hex` function on `LeafVersion`.
Remove the feature gate from the macro and put it on the individual
call sites as needed.
Potentially the whole `pow` module will move to `primitives` but this
is not possible easily right now. However, we would like to be able to
move the `BlockHash` and `block::Header` types over to `primitives`
and doing so requires the `CompactTarget` to be there.
Move the `CompactTarget` type to `primitives` and re-export it from the
`primitives` crate root.
Note also, we re-export the type publicly from `bitcoin::pow`.