pth: run make test

If pth is miscompiled, other software that uses it can fail
mysteriously without a clear indication of the source of the
problem. This causes problems with gnupg2 on some platforms,
for example.

pth's `make test` will reveal this kind of problem, so always run
that to be safe.

See: mistydemeo/tigerbrew#39.

Formula/pth.rb

@@ -12,6 +12,8 @@ class Pth < Formula
     system "./configure", "--disable-dependency-tracking",
                           "--prefix=#{prefix}",
                           "--mandir=#{man}"
+    system "make"
+    system "make test"
     system "make install"
   end
 end