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

init.c

@@ -43,9 +43,6 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 #include "busybox.h"
-#define bb_need_full_version
-#define BB_DECLARE_EXTERN
-#include "messages.c"
 #ifdef BB_SYSLOGD
 # include <sys/syslog.h>
 #endif