Patch review for fix to #947 (assert on SIGHUP to varnishncsa)

[Tollef Fog Heen]

]] Martin Blix Grydeland 

| This bug is caused by an assert when usleep is interrupted by signal
| delivery in vsl.c (libvarnishapi). Some tools expect to receive signals
| (e.g. varnishncsa with -w option), so this has to be addressed. Attached
| patch relaxes the assert to not trigger on signal interrupt. Any comments
| appreciated.

Looks reasonable to me, please commit.

Regards,
-- 
Tollef Fog Heen
Varnish Software
t: +47 21 98 92 64