ephy-download: Detect .xz as compressed too

A fix to a hack to avoid filenames like "filename.tar(1).xz"

https://bugzilla.gnome.org/show_bug.cgi?id=711750
ephy-history-view: Call parent class on button release handler

https://bugzilla.gnome.org/show_bug.cgi?id=696653
uri-tester: Avoid critical when unref-ing NULL regex

When a regex compilation fails we get an error and NULL. No need to
unref the NULL pointer.

https://bugzilla.gnome.org/show_bug.cgi?id=719405
uri-tester: Compile regex in JavaScript compatibility mode

AddBlock regexes now are compiled in JavaScript compatibility mode to
avoid the errors happening from using the patterns from
https://easylist-downloads.adblockplus.org/easylist.txt .

https://bugzilla.gnome.org/show_bug.cgi?id=719399