hgweb: look up "URLSearchParams" in "window" to work around jshint issues
Unfortunately, current version of jshint (2.9.5) doesn't know such a global
variable and complains that it's undefined. Since this line tries to look up
URLSearchParams in a global scope (i.e. window), let's simply preface it with
"window." to work around jshint.
$ hg init
$ echo This is file a1 > a
$ hg add a
$ hg commit -m "commit #0"
$ ls
a
$ echo This is file b1 > b
$ hg add b
$ hg commit -m "commit #1"
$ hg co 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
B should disappear
$ ls
a