Support multlined array environment

[sylph1o]

This simply adds multlined (from the amsmath package) to the list of math array environments. Note that I don't actually know Perl, I just copied #116 and it seems to work.

[ftilmann]

Thanks. If you can copy here an equation making use of the multlined environment, I could add it to the test cases.

[sylph1o]

Thanks for the quick merge. Here is a working example.

\documentclass{article}

\usepackage{amsmath}
\usepackage{mathtools}

\begin{document}
\begin{align}
  a & = b + c \\
  c & =
      \begin{multlined}[t]
        d + e + f + g + h + i + j \\
        + k + l + m + n + o + p + q
      \end{multlined}
\end{align}
\end{document}