Move messages.c to libbb. Make each string in messages.c be its own .o file.

This way, we can new get rid of all that tedious #define rubbish we used to
need to enable specific messages.  This way is enormously simpler, and as a
bonus also ends up saving us 96 bytes.
 -Erik

applets/busybox.c

@@ -5,11 +5,6 @@
 #include <errno.h>
 #include <stdlib.h>
 #include "busybox.h"
-
-#define bb_need_full_version
-#define BB_DECLARE_EXTERN
-#include "messages.c"
-
 #ifdef BB_LOCALE_SUPPORT
 #include <locale.h>
 #endif