[jsapi-utils] Add support for doubles
[jsapi-utils] Add support for doubles

Add support for doubles using the 'f' specifier

https://bugzilla.gnome.org/show_bug.cgi?id=610320

joeshaw/gjs,joeshaw/gjs,endlessm/gjs,magcius/gjs,endlessm/gjs,pixunil/cjs,djdeath/gjs,magcius/gjs,mtwebster/cjs,endlessm/gjs,pixunil/cjs,endlessm/gjs,djdeath/gjs,mtwebster/cjs,magcius/gjs,magcius/gjs,djdeath/gjs,djdeath/gjs,endlessm/gjs,mtwebster/cjs,pixunil/cjs,djdeath/gjs,joeshaw/gjs,magcius/gjs,pixunil/cjs,joeshaw/gjs,mtwebster/cjs,mtwebster/cjs,pixunil/cjs,joeshaw/gjs