Minor C cleanup (#27)

* Minor C cleanup

 - some symbols can be made static:
    1. set_gov_state
    2. everything in gamemode_client.h
 - daemonize() can also take a const char*, since the name is only
   passed to printf() or syslog()
 - prevent shadowing of variables
 - use explicit (void) as parameter-list more consistently
 - use some more const.
   Move cast to more appropriate place and document that execv() behaves
   as if args where of type const *char and we trust on that.
 - example: Just use main(void), which is also an acceptable ISO-C decl
 - example: Use stderr for errors

* Fix -Wold-style-declaration issue

daemon/daemonize.c

@@ -39,7 +39,7 @@ POSSIBILITY OF SUCH DAMAGE.
 /**
  * Helper to perform standard UNIX daemonization
  */
-void daemonize(char *name)
+void daemonize(const char *name)
 {
 	/* Initial fork */
 	pid_t pid = fork();