Move daemonize handling to OS specific files

Move daemonize handling from vl.c to OS specific files. Provide dummy
stubs for Win32.

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Acked-by: Juan Quintela <quintela@redhat.com>
Acked-by: Richard Henderson <rth@redhat.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

os-win32.c

@@ -214,3 +214,8 @@ void os_parse_cmd_args(int index, const char *optarg)
 {
     return;
 }
+
+void os_pidfile_error(void)
+{
+    fprintf(stderr, "Could not acquire pid file: %s\n", strerror(errno));
+}