If someone manages to open a file before rtems_libio_post_driver is run,
open() may allocate a file number other than 0 for stdin. This leads to
a silent failure of the logic in rtems_libio_post_driver, and confusing
behavior because your BSP behaves as if it doesn't have a console.
Instead of failing silently, raise an internal error if open() succeeds
but gives us an unexpected file number for stdin.
Script does what is expected and tries to do it as
smartly as possible.
+ remove occurrences of two blank comment lines
next to each other after Id string line removed.
+ remove entire comment blocks which only exited to
contain CVS Ids
+ If the processing left a blank line at the top of
a file, it was removed.
