libsoup: bump version

Closes #349.

Attached patch updates libsoup to version 2.26.2.

This is relevant for bug 303 as it allows to compile gvfs with much
less patching.

Signed-off-by: Sven Neumann <s.neumann@raumfeld.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>