Fixes for crashes running readelf.

Fixes for crashes running readelf.

	PR binutils/17531
	* readelf.c (get_data): If the reason parameter is null, do not
	print any error messages.
	(get_32bit_section_headers): Verify section header entry size
	before reading in the section headers.
	(get_64bit_section_headers): Likewise.
	(process_section_headers): Pass FALSE to get_section_headers.
	(get_file_header): Pass TRUE to get_section_headers.
	(process_dynamic_section): Change an assert to an error message.
	(process_symbol_table): Handle corrupt histograms.