Revise sleb128 and uleb128 reader

This patch catches and reports errors when reading leb128 values,
addressing a FIXME in read_leb128.

	* dwarf.h (read_leb128): Update prototype.
	(report_leb_status): New inline function.
	(SKIP_ULEB, SKIP_SLEB, READ_ULEB, READ_SLEB): Define.
	* dwarf.c: Use above macros throughout file.  Formatting.
	(read_leb128): Reorder params.  Add status return param.
	Don't stop reading until finding terminator or end of data.
	Detect loss of significant bits.  Sign extend only on
	terminating byte.
	(read_sleb128, read_uleb128): Delete functions.
	(SKIP_ULEB, SKIP_SLEB, READ_ULEB, READ_SLEB): Delete macros.
	(read_and_print_leb128): Rewrite.
	(process_extended_line_op): Return a size_t.  Use size_t vars.
	Adjust to suit new macros.  Add proper name size to "data" when
	processing DW_LNE_define_file.
	(process_abbrev_section): Adjust to suit new macros.
	(decode_location_expression, skip_attr_bytes): Likewise.
	(get_type_signedness): Likewise.
	(read_and_display_attr_value): Likewise.  Consolidate block code.
	(process_debug_info): Adjust to suit new macros.
	(display_formatted_table, display_debug_lines_raw): Likewise.
	(display_debug_lines_decoded): Likewise.  Properly check for end
	of DW_LNS_extended_op.
	(display_debug_macinfo): Adjust to suit new macros.
	(get_line_filename_and_dirname, display_debug_macro): Likewise.
	(display_view_pair_list): Likewise.  Don't back off when hitting
	end of data.
	(display_loc_list): Adjust to suit new macros.
	(display_loclists_list, display_loc_list_dwo): Likewise.
	(display_debug_rnglists_list, read_cie): Likewise.
	(display_debug_frames): Likewise.
	* readelf.c: Use new ULEB macros throughout file.
	(read_uleb128): Delete.
	(decode_arm_unwind_bytecode): Use read_leb128.
	(decode_tic6x_unwind_bytecode): Likewise.
	(display_tag_value): Adjust to suit new macros.
	(display_arc_attribute, display_arm_attribute): Likewise.
	(display_gnu_attribute, display_power_gnu_attribute): Likewise.
	(display_s390_gnu_attribute, display_sparc_gnu_attribute): Likewise.
	(display_mips_gnu_attribute, display_tic6x_attribute): Likewise.
	(display_msp430x_attribute, display_msp430_gnu_attribute): Likewise.
	(display_riscv_attribute, process_attributes): Likewise.