cpukit, testsuite: Add rtems_printf and rtems_printer support.

This change adds rtems_printf and related functions and wraps the
RTEMS print plugin support into a user API. All references to the
plugin are removed and replaced with the rtems_printer interface.

Printk and related functions are made to return a valid number of
characters formatted and output.

The function attribute to check printf functions has been added
to rtems_printf and printk. No changes to remove warrnings are part
of this patch set.

The testsuite has been moved over to the rtems_printer. The testsuite
has a mix of rtems_printer access and direct print control via the
tmacros.h header file. The support for begink/endk has been removed
as it served no purpose and only confused the code base. The testsuite
has not been refactored to use rtems_printf. This is future work.

testsuites/samples/capture/init.c

@@ -27,6 +27,7 @@ rtems_task Init(rtems_task_argument argument);
 static void notification(int fd, int seconds_remaining, void *arg);
 
 const char rtems_test_name[] = "CAPTURE ENGINE";
+rtems_printer rtems_test_printer;
 
 volatile int can_proceed = 1;
 
@@ -46,6 +47,7 @@ rtems_task Init(
   rtems_task_priority old_priority;
   rtems_mode          old_mode;
 
+  rtems_print_printer_printf(&rtems_test_printer);
   rtems_test_begin();
 
   status = rtems_shell_wait_for_input(