This removes all usage of SpiderMonkey API that is deprecated in mozjs24 and will be removed in mozjs31. https://bugzilla.gnome.org/show_bug.cgi?id=742249
jsapi.h has some bad warnings with gcc. gjs-module.h already includes jsapi.h and uses a complicated set of GCC pragmas to mask them out, so just kill our include.
https://bugzilla.gnome.org/show_bug.cgi?id=711052