Valgrind: sigaction() failure now ignored.
Valgrind: sigaction() failure now ignored.

Valgrind intercepts SIGUSR2 in some cases, and nginx might not be able to
start due to sigaction() failure.  If compiled with NGX_VALGRIND defined,
we now ignore the failure of sigaction().

firebase/nginx,firebase/nginx,firebase/nginx,hy0kl/nginx,hy0kl/nginx,hy0kl/nginx,firebase/nginx