Win32: added missing call to srand().

Found by Veracode.

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 c3dfec9..cf73d82 100644
--- a/src/os/win32/ngx_win32_init.c
+++ b/src/os/win32/ngx_win32_init.c
@@ -228,6 +228,8 @@
         ngx_sprintf((u_char *) ngx_unique, "%P%Z", ngx_pid);
     }
 
+    srand((unsigned) ngx_time());
+
     return NGX_OK;
 }