Fix load_url threading permissions in GTK Add GTK version declarations
Fix load_url threading permissions in GTK
Add GTK version declarations

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