libtasn1: run `make check`

`libtasn1` is used for crypto apps (e.g. `gnutls`), so we should
probably make sure it works properly.

Formula/libtasn1.rb

@@ -18,6 +18,7 @@ class Libtasn1 < Formula
   def install
     system "./configure", "--prefix=#{prefix}", "--disable-dependency-tracking",
                           "--disable-silent-rules"
+    system "make", "check"
     system "make", "install"
   end