Updates qutebrowser: 63fb51f Updates dist, adds qutebrowser-exec for session handling

diff --git a/qutebrowser b/qutebrowser
index bf6014f52e34b0e4181039592877039acb80b6df..63fb51fa5737f99dd69f122bdac5493d3360008b 160000 (submodule)
--- a/qutebrowser
+++ b/qutebrowser
@@ -1 +1 @@
-Subproject commit bf6014f52e34b0e4181039592877039acb80b6df
+Subproject commit 63fb51fa5737f99dd69f122bdac5493d3360008b