Issue 5201 - [emscripten] Replace EM_ASM calls by a custom JavaScript library

compiled/String.h

 /*
  * 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/>.
  */
 
 #pragma once
 
 #include <algorithm>
 #include <cstddef>
 #include <cstring>
 #include <type_traits>
 
-#include <emscripten.h>
-
 #include "debug.h"
-
-extern "C"
-{
-  // It seems that calling JS is the easiest solution for lowercasing Unicode
-  // characters.
-  char16_t CharToLower(char16_t charCode);
-}
+#include "library.h"
 
 inline void String_assert_readonly(bool readOnly);
 
 class String
 {
   friend class DependentString;
   friend class OwnedString;
 
 public:
   typedef char16_t value_type;
@@ skipping 361 matching lines @@
     if (negative)
       mBuf[pos++] = '-';
 
     for (int i = size - 1; i >= 0; i--)
     {
       mBuf[pos + i] = '0' + (num % 10);
       num /= 10;
     }
   }
 };