Per PR47 add support for buffered test output. This involved
adding defines to redirect output to a buffer and dump it when
full, at "test pause", and at exit. To avoid problems when redefining
exit(), all tests were modified to call rtems_test_exit().
Some tests, notable psxtests, had to be modified to include
the standard test macro .h file (pmacros.h or tmacros.h) to
enable this support.