Introduce C++ templates replacements for DEFINE_INTERFACE_X and RegisterFunction macros

The new methods:
- aren't included in ScriptInterface.h directly, lightening that header
- don't use boost CPP
- don't need argument types or number or constness to be specified
- can work with object methods somewhat transparently
- support optional cmptPrivate (allowing removal of many UNUSED macro)
- support optional const ScriptRequest&, which is safer.

This first diff changes only some of the JSI files & the component
manager. Further diffs will update other files and finally delete the
current code.

Differential Revision: https://code.wildfiregames.com/D2818
This was SVN commit r24969.

source/scriptinterface/ScriptInterface.cpp

@@ -72,7 +72,7 @@ struct ScriptInterface_impl
 };
 
 ScriptRequest::ScriptRequest(const ScriptInterface& scriptInterface) :
-	cx(scriptInterface.m->m_cx)
+	cx(scriptInterface.m->m_cx), nativeScope(scriptInterface.m->m_nativeScope)
 {
 	m_formerRealm = JS::EnterRealm(cx, scriptInterface.m->m_glob);
 	glob = JS::CurrentGlobalOrNull(cx);