Be careful about square brackets inside \item[...].

We were generating:

\item[\textjapanese[]{...}]

which was causing LaTeX errors because the lookahead for the `]` is
very fragile.  Adding braces is sufficient to fix the problem:

\item[{\textjapanese{}{...}}]

We also suppress the square brackets after a language change where
it's not necessary, and fix a similar potential problem with section
headings.

Change-Id: Ic147bef36848110ce1dfe1254f1f7b1a8b675fe0