Added per-process random seeding (ticket #456).

src/os/unix/ngx_process_cycle.c

diff --git a/src/os/unix/ngx_process_cycle.c b/src/os/unix/ngx_process_cycle.c
index 9d23a73..499039a 100644
--- a/src/os/unix/ngx_process_cycle.c
+++ b/src/os/unix/ngx_process_cycle.c
@@ -959,6 +959,8 @@
                       "sigprocmask() failed");
     }
 
+    srandom((ngx_pid << 16) ^ ngx_time());
+
     /*
      * disable deleting previous events for the listening sockets because
      * in the worker processes there are no events at all at this point

src/os/win32/ngx_win32_init.c

diff --git a/src/os/win32/ngx_win32_init.c b/src/os/win32/ngx_win32_init.c
index d2505ce..d3cc376 100644
--- a/src/os/win32/ngx_win32_init.c
+++ b/src/os/win32/ngx_win32_init.c
@@ -228,7 +228,7 @@
         ngx_sprintf((u_char *) ngx_unique, "%P%Z", ngx_pid);
     }
 
-    srand((unsigned) ngx_time());
+    srand((ngx_pid << 16) ^ (unsigned) ngx_time());
 
     return NGX_OK;
 }