Arm Ehdr flag printing

Arm Ehdr flag printing

Arm needs to decode flags and I modeled it after the binutils code.
The same messages are printed.  Given the requirement of the interface
and the ABIs the current version of the callback function isn't
sufficient unless one wants to create a stateful interface.  The
problem is that most flags need to be interpreted in the context of
the ABI version.  So I changed the API to also pass the original flag
value.  This shouldn't be a problem because there are no users yet.

There is also a bug in ebl_machine_flag_name. When copying the string
provided by the callback cp is moved past the NUL byte.  It should
move to the NUL byte.  Otherwise one cannot anything but the first
added flag description.  Finally some cosmetic changes (space after
each comma in the output).

Signed-off-by: Mark Wielaard <mark@klomp.org>