close the DATA handles when done with them

See http://www.cpantesters.org/cpan/report/25449004

At some point in t/metasyntactic.t, all themes started failing
with a "Too many open files at (eval 1234) line 1."

Since, according to perldata,

    The filehandle is left open pointing to the contents after __DATA__.
    It is the program's responsibility to "close DATA" when it is done
    reading from it.

it is very likely that closing DATA when done with it will fix this issue.
Changes for version 1.008