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

compiled/bindings/runtime_utils.cpp

-#include <emscripten.h>
-
+#include "runtime.h"
 #include "../intrusive_ptr.h"
 #include "../String.h"
 
 extern "C"
 {
-  void EMSCRIPTEN_KEEPALIVE InitString(DependentString* str,
+  void BINDINGS_EXPORTED InitString(DependentString* str,
       String::value_type* data, String::size_type len)
   {
     // String is already allocated on stack, we merely need to call
     // constructor.
     new (str) DependentString(data, len);
   }
 
-  void EMSCRIPTEN_KEEPALIVE DestroyString(OwnedString* str)
+  void BINDINGS_EXPORTED DestroyString(OwnedString* str)
   {
     // Stack memory will be freed automatically, we need to call
     // destructor explicitly however.
     str->~OwnedString();
   }
 
-  String::size_type EMSCRIPTEN_KEEPALIVE GetStringLength(
+  String::size_type BINDINGS_EXPORTED GetStringLength(
       const String& str)
   {
     return str.length();
   }
 
-  const String::value_type* EMSCRIPTEN_KEEPALIVE GetStringData(
+  const String::value_type* BINDINGS_EXPORTED GetStringData(
       const String& str)
   {
     return str.data();
   }
 
-  void EMSCRIPTEN_KEEPALIVE ReleaseRef(ref_counted* ptr)
+  void BINDINGS_EXPORTED ReleaseRef(ref_counted* ptr)
   {
     ptr->ReleaseRef();
   }
 }