Plug another left shift of a negative value
Plug another left shift of a negative value

From upstream:

Avoid left shift of a negative value in flush rank calculation.
The C standard permits an undefined result for a left shift of a
negative value.

feld/Varnish-Cache,feld/Varnish-Cache,gquintard/Varnish-Cache,feld/Varnish-Cache,feld/Varnish-Cache,gquintard/Varnish-Cache,gquintard/Varnish-Cache,gquintard/Varnish-Cache,feld/Varnish-Cache