Issue 5216 - [emscripten] Use a more reliable way of retrieving mangled function name

compiled/bindings/library.js

+/*
+ * This file is part of Adblock Plus <https://adblockplus.org/>,
+ * Copyright (C) 2006-2017 eyeo GmbH
+ *
+ * Adblock Plus is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * Adblock Plus is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+"use strict";
+
+mergeInto(LibraryManager.library, {
+  GetFunctionName__asm: true,
+  GetFunctionName__sig: [],
+  GetFunctionName: function(buffer, ptr, signature)
+  {
+    var table = eval("FUNCTION_TABLE_" + AsciiToString(signature));
+    var name = table[HEAP32[ptr >> 2] % table.length].name;
+    if (buffer)
+      stringToAscii(name, buffer);
+    return name.length + 1;
+  }
+});