Code tags

This pull request assumes that the resulting XML documentation will be processed by [SHFB](https://shfb.codeplex.com/). I felt this assumption was reasonable because the current use of `<inheritdoc/>` already requires that.

* When documenting a method with a parameter named `foo`, translate `{@code foo}` to `<paramref name="foo"/>` instead of `<code>foo</code>`
* Translate `{@code true}` to `<see langword="true"/>` (SHFB-specific syntax as noted in the link in e84805d)
* Translate `{@code ...}` to `<c>...</c>` instead of `<code>...</code>`
* XML-escape literal `<` and `>` characters that appear within a `{@code ...}` tag, similar to the way the Javadoc tool itself processes these characters within the tag