cppcheck 1.56

Closes Homebrew/homebrew#14960.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Formula/cppcheck.rb

@@ -2,8 +2,8 @@ require 'formula'
 
 class Cppcheck < Formula
   homepage 'http://sourceforge.net/apps/mediawiki/cppcheck/index.php?title=Main_Page'
-  url 'https://github.com/danmar/cppcheck/tarball/1.55'
-  sha1 '5a888427b9303420a1a583a2cb3919fb5ba3c5ce'
+  url 'https://github.com/danmar/cppcheck/tarball/1.56'
+  sha1 '195e8c819bff51bf2242133851052105a0619bf0'
 
   head 'https://github.com/danmar/cppcheck.git'
 
@@ -39,6 +39,10 @@ class Cppcheck < Formula
     end
   end
 
+  def test
+    system "#{bin}/cppcheck", "--version"
+  end
+
   def caveats; <<-EOS.undent
     --with-gui installs cppcheck-gui.app in:
       #{bin}