SoupContentSniffer: removed several unused function arguments
SoupContentSniffer: removed several unused function arguments

Removed the SoupMessage argument from various sniffing functions as it isn't
really used for sniffing.

https://bugzilla.gnome.org/show_bug.cgi?id=682112

Distrotech/libsoup,jwendell/libsoup,jwendell/libsoup,Distrotech/libsoup,jwendell/libsoup,Distrotech/libsoup,Distrotech/libsoup,fanc999/libsoup,Distrotech/libsoup,jwendell/libsoup,fanc999/libsoup,fanc999/libsoup,fanc999/libsoup,jwendell/libsoup,fanc999/libsoup