Make it a `const` instead of referencing the value in the system library
to save a relocation.

Fix the build failure.

I agree to license my contributions to each file under the terms given
at the top of each file I changed.

Add AEAD decryption benchmarks

Prepare for the removal of the `PartialEq`/`Eq` implementations from
`untrusted`. The goal of such removal is to make timing leaks more
obvious, and to make the absense of timing leaks more clear.

It isn't useful for it to be in the crate, as it isn't used in any part of the
build or tests.

Take a step towards having RSA keys support encryption/decryption
in addition to signing/verification.

No functional changes are intended.

Some documentation was moved around.

This should allow tests to pass on the crates.io release.

The `let _ =` stuff makes it look like we're ignoring the result. It
isn't clear that `with_bad_i` was doing the check we needed. Merge
`with_good_i` and `with_bad_i` into one `with_i` and move the checks to
the calling code.

`big_endian_without_leading_zero_as_input().as_slice_less_safe()` is
equivalent to `big_endian_without_leading_zero()`. Simplify users of the
former to use the latter.

This facilitates moving the unit tests to integration tests.

Simplify the integer parsing code. Instead of jumping through hoops to use
the `untrusted` API for validating the syntax, take advantage of slice
patterns, which weren't available at the time the original code was written.

Eliminate redundancy in checking for non-zero values when parsing positive
integers.

Use normal error handling instead of panicking. That is, don't require/assume that the caller
of `io::Positive::new_non_empty_without_leading_zeros()` already validated the input. This
adds redundant error checking when it is used by `io::der`, but will simplify (future)
callers outside of `io::der`.

Rename the function.

Follow the Rust convention of having minimal constraints on type
definitions.

Prepare for a future where the `rsa` module is public. (Currently this is a no-op
since `rsa` isn't public.)

Prepare for making the `rsa` module public.

No semantic change; using `skip_to_end()` is just clearer.