Adds Genode::Hex_dump class to the formatted_output.h header. This class can be
used to print a hexadecimal dump of a byte range. The data is printed in a
format similar to that used by Linux's 'xxd'. In addition to the 'xxd' format,
consecutive duplicate lines are replaced with a single "*\n" as done also by
Linux's 'hexdump'.
Ref #4966
The utilities of the new util/formatted_output.h header complement the
existing base/output.h with the text-formatting support needed to
produce tabular output.
Fixes#4449
