Move printer initialization to separate header

The RTEMS print user need to know nothing about a particular printer
implementation.  In particular get rid of the <stdio.h> include which
would be visible via <rtems.h>.

cpukit/libdl/rap.c

@@ -19,6 +19,7 @@
 #include "config.h"
 #endif
 
+#include <stdarg.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>