security: rtrim, not unsafe /X+$/ idiom

Problem:
replace(/X+$/, '') is vulnerable to REDOS

Solution:
Replace all instances I could find with a custom rtrim

lib/marked.js

@@ -217,7 +217,7 @@ Lexer.prototype.token = function(src, top) {
       this.tokens.push({
         type: 'code',
         text: !this.options.pedantic
-          ? cap.replace(/\n+$/, '')
+          ? rtrim(cap, '\n')
           : cap
       });
       continue;
@@ -1303,7 +1303,7 @@ function resolveUrl(base, href) {
     if (/^[^:]+:\/*[^/]*$/.test(base)) {
       baseUrls[' ' + base] = base + '/';
     } else {
-      baseUrls[' ' + base] = base.replace(/[^/]*$/, '');
+      baseUrls[' ' + base] = rtrim(base, '/', true);
     }
   }
   base = baseUrls[' ' + base];
@@ -1355,6 +1355,38 @@ function splitCells(tableRow, count) {
   return cells;
 }
 
+// Return str with all trailing {c | all but c} removed
+// allButC: Default false
+function rtrim(str, c, allButC) {
+  if (typeof allButC === 'undefined') {
+    allButC = false;
+  } else {
+    allButC = true;
+  }
+  var mustMatchC = !allButC;
+
+  if (str.length === 0) {
+    return '';
+  }
+
+  // ix+1 of leftmost that fits description
+  // i.e. the length of the string we should return
+  var curr = str.length;
+
+  while (curr > 0) {
+    var currChar = str.charAt(curr - 1);
+    if (mustMatchC && currChar === c) {
+      curr--;
+    } else if (!mustMatchC && currChar !== c) {
+      curr--;
+    } else {
+      break;
+    }
+  }
+
+  return str.substr(0, curr);
+}
+
 /**
  * Marked
  */