[Cocoa] Make confirm_quit an instance attribute
[Cocoa] Make confirm_quit an instance attribute

We might need seperate confirm_quit options for each window. This also
gets rid of the global variable.

shivaprsdv/pywebview,r0x0r/pywebview,r0x0r/pywebview,r0x0r/pywebview,shivaprsdv/pywebview,r0x0r/pywebview,shivaprsdv/pywebview,r0x0r/pywebview,shivaprsdv/pywebview