filter: use regexp to check multipart bodies

This should be safer than running file(1), which has had its share
of vulnerabilities this year (early 2014) We really only care about
diffs and maybe short log files, here.

1 files changed, 2 insertions, 0 deletions

diff --git a/t/filter.t b/t/filter.t
index 0aa26a5f..ac9f1f6f 100644
--- a/t/filter.t
+++ b/t/filter.t
@@ -291,6 +291,8 @@ int main(void)
         printf("Hello world\\n");
         return 0;
 }
+
+/* some folks like ^L */
 EOF
                 ),
                 Email::MIME->create(