[markdown mode] Don't allow backslash-escaping in code fragments

Closes #3800

mode/markdown/markdown.js

@@ -376,15 +376,6 @@ CodeMirror.defineMode("markdown", function(cmCfg, modeCfg) {
 
     var ch = stream.next();
 
-    if (ch === '\\') {
-      stream.next();
-      if (modeCfg.highlightFormatting) {
-        var type = getType(state);
-        var formattingEscape = tokenTypes.formatting + "-escape";
-        return type ? type + " " + formattingEscape : formattingEscape;
-      }
-    }
-
     // Matches link titles present on next line
     if (state.linkTitle) {
       state.linkTitle = false;
@@ -420,6 +411,15 @@ CodeMirror.defineMode("markdown", function(cmCfg, modeCfg) {
       return getType(state);
     }
 
+    if (ch === '\\') {
+      stream.next();
+      if (modeCfg.highlightFormatting) {
+        var type = getType(state);
+        var formattingEscape = tokenTypes.formatting + "-escape";
+        return type ? type + " " + formattingEscape : formattingEscape;
+      }
+    }
+
     if (ch === '!' && stream.match(/\[[^\]]*\] ?(?:\(|\[)/, false)) {
       stream.match(/\[[^\]]*\]/);
       state.inline = state.f = linkHref;