Allow \n@ inside inline tags.

For historical reasons, the standard doclet first breaks a doc comment into body text and block tags, where each block tag is defined by beginning with `@` at the beginning of a line (ignoring whitespace and asterisks etc).
Inline tags are not taken into account when looking for block tags.

This makes it difficult to use annotations inside `{@code...}` because annotations are typically also placed at the beginning of a line.

Separately, it is already the case that there is barely-documented support in inline tags to "skip over " balanced pairs of `{ }` when looking for the `}` that terminates the inline tag.

It may be reasonable extend inline tags to allow `@` at the beginning of a line. In other words, when looking for block tags, we should not be looking inside open inline tags.