remove old Opera-specific CSS properties where Opera supports the standard properties.

lib/codemirror.css

@@ -166,7 +166,7 @@ div.CodeMirror span.CodeMirror-nonmatchingbracket {color: #f22;}
 }
 .CodeMirror pre {
   /* Reset some styles that the rest of the page might have set */
-  -moz-border-radius: 0; -webkit-border-radius: 0; -o-border-radius: 0; border-radius: 0;
+  -moz-border-radius: 0; -webkit-border-radius: 0; border-radius: 0;
   border-width: 0;
   background: transparent;
   font-family: inherit;

theme/ambiance-mobile.css

 .cm-s-ambiance.CodeMirror {
   -webkit-box-shadow: none;
   -moz-box-shadow: none;
-  -o-box-shadow: none;
   box-shadow: none;
 }

theme/ambiance.css

@@ -46,7 +46,6 @@
   background-color: #202020;
   -webkit-box-shadow: inset 0 0 10px black;
   -moz-box-shadow: inset 0 0 10px black;
-  -o-box-shadow: inset 0 0 10px black;
   box-shadow: inset 0 0 10px black;
 }