be: Improve flag dumping code
be: Improve flag dumping code

- Always dump the actual name and not some apreviation/interpretation.
- Add the missing flags.
- Use a switch so we get a warning when flags are missing from the list.

MatzeB/libfirm,MatzeB/libfirm,libfirm/libfirm,libfirm/libfirm,MatzeB/libfirm,MatzeB/libfirm,libfirm/libfirm,libfirm/libfirm,MatzeB/libfirm,libfirm/libfirm,MatzeB/libfirm,MatzeB/libfirm