[mbo theme] Remove background-blocking styles

Closes #2623

Author: marijnh

demo/matchtags.html

@@ -11,7 +11,6 @@
 <script src="../mode/xml/xml.js"></script>
 <style type="text/css">
       .CodeMirror {border-top: 1px solid black; border-bottom: 1px solid black;}
-      .CodeMirror-matchingtag { background: rgba(255, 150, 0, .3); }
     </style>
 <div id=nav>
   <a href="http://codemirror.net"><img id=logo src="../doc/logo.png"></a>

lib/codemirror.css

@@ -129,6 +129,7 @@ div.CodeMirror-overwrite div.CodeMirror-cursor {}
 
 div.CodeMirror span.CodeMirror-matchingbracket {color: #0f0;}
 div.CodeMirror span.CodeMirror-nonmatchingbracket {color: #f22;}
+.CodeMirror-matchingtag { background: rgba(255, 150, 0, .3); }
 .CodeMirror-activeline-background {background: #e8f2ff;}
 
 /* STOP */

theme/mbo.css

@@ -22,15 +22,15 @@
 .cm-s-mbo span.cm-bracket {color: #fffffc; font-weight: bold;}
 .cm-s-mbo span.cm-tag {color: #9ddfe9;}
 .cm-s-mbo span.cm-link {color: #f54b07;}
-.cm-s-mbo span.cm-error {background: #636363; color: #ffffec;}
+.cm-s-mbo span.cm-error {border-bottom: #636363; color: #ffffec;}
 
 .cm-s-mbo .CodeMirror-activeline-background {background: #494b41 !important;}
 .cm-s-mbo .CodeMirror-matchingbracket {
   text-decoration: underline;
   color: #f5e107 !important;
  }
 
-.cm-s-mbo .CodeMirror-matchingtag {background: #4e4e4e;}
+.cm-s-mbo .CodeMirror-matchingtag { background: rgba(255, 255, 255, .37); }
 
 .cm-s-mbo span.cm-searching {
   background-color: none;