function: Add argument names to our function's toString
function: Add argument names to our function's toString

It's sometimes hard to know what each argument is when translated to JS. This
should provide a helpful debugging hint for those new to the GNOME JS dev
process, and also help with debugging hard errors about wrong argument types.

https://bugzilla.gnome.org/show_bug.cgi?id=676833

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