[KEEP IN SYNC WITH SPIDERMONKEY.H]

Master header for the SpiderMonkey Javascript library.

Include this instead of accessing any <js*.h> headers directly. Rationale: they require an OS macro to be set (XP_*). Since this is specific to SpiderMonkey, we don't want to saddle another obscure header with it (would make reuse harder). Instead, do it here where the purpose is clear.

This doesn't go in ScriptingHost.h because some other files (notably precompiled.h and i18n/ScriptInterface.cpp) want only these definitions without pulling in the whole of ScriptingHost.