[SM68 2/2] Update to Spidermonkey 68 APIs

No noteworthy API changes.

Details:
- Remove UTF16 script execution since UTF8 is supported in SM68 and
going forward
- Several new headers includes are required
- Realms replace Compartments as "global holders" (see meta-Bug 1357862)
- JSRequests are removed entirely (Bug 722345), see also aae417bd29
- Trivial API updates in ProxyHandlers, ArrayBuffer, Warnings, GC
reasons, Context options, ObjectIsFunction, ValueVectors and
JSCompartment

See also the migration guide:
https://github.com/mozilla-spidermonkey/spidermonkey-embedding-examples/blob/esr78/docs/Migration%20Guide.md

Tested by: Freagarach, Stan, Subitaneo
Fixes #5860

Differential Revision: https://code.wildfiregames.com/D3144
This was SVN commit r24297.

source/scriptinterface/ScriptConversions.cpp

@@ -18,6 +18,7 @@
 #include "precompiled.h"
 
 #include "ScriptConversions.h"
+#include "ScriptExtraHeaders.h"
 
 #include "graphics/Entity.h"
 #include "maths/Vector2D.h"
@@ -28,7 +29,7 @@
 #define FAIL(msg) STMT(LOGERROR(msg); return false)
 
 // Implicit type conversions often hide bugs, so warn about them
-#define WARN_IF_NOT(c, v) STMT(if (!(c)) { JS_ReportWarningUTF8(rq.cx, "Script value conversion check failed: %s (got type %s)", #c, JS::InformalValueTypeName(v)); })
+#define WARN_IF_NOT(c, v) STMT(if (!(c)) { JS::WarnUTF8(rq.cx, "Script value conversion check failed: %s (got type %s)", #c, JS::InformalValueTypeName(v)); })
 
 template<> bool ScriptInterface::FromJSVal<bool>(const ScriptRequest& rq, JS::HandleValue v, bool& out)
 {