Style: fix differences in padding between highlighted/non-highlighted

_includes/head.html

@@ -8,6 +8,9 @@
 
   <title>C++ Core Guidelines</title>
 
+  <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.9.0/styles/github.min.css">
+  <script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.9.0/highlight.min.js"></script>
+
   <!-- CSS, could be merged and minified for improved loading speed -->
   <link rel="stylesheet" href="{{ site.baseurl }}/public/css/poole.css">
   <link rel="stylesheet" href="{{ site.baseurl }}/public/css/syntax.css">
@@ -17,9 +20,6 @@
   <link rel="stylesheet" type="text/css" href="https://fonts.googleapis.com/css?family=PT+Sans:400,400italic,700|Abril+Fatface|Roboto+Mono">
   <meta name="description" content="{% if page.excerpt %}{{ page.excerpt | strip_html | strip_newlines | truncate: 160 }}{% else %}{{ site.description }}{% endif %}">
 
-  <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.9.0/styles/github.min.css">
-  <script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.9.0/highlight.min.js"></script>
-
 
   <!-- Include jquery.js -->
   <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>

public/css/custom.css

@@ -33,6 +33,12 @@
   background: url('../images/icon_download.png') no-repeat 0% 90%;
 }
 
+/** same style for highlighted, non-highlight */
+.cpp.hljs {
+    overflow-x: unset;
+    padding: unset;
+}
+
 .zip_download_link {
   display: block;
   float: right;