* elf/readelf.c (process_dynamic_segment): Print DT_* value only if

* elf/readelf.c (process_dynamic_segment): Print DT_* value only if
do_dynamic.
(do_histogram): New variable.
(options): New long option histogram.  Set do_histogram if this
option is used.
(usage): Document --histogram.
(parse_args): Handle 0 return value from getopt_long.  Enable
do_histogram for -a.
(process_symbol_table): Read hash table also if only do_histogram.
Add code to print hash table histogram.