* defs.h (enum misc_command_type, command_control_type): Enums

	* defs.h (enum misc_command_type, command_control_type): Enums
	for describing the command and control types.
	(struct command_line): Add new fields to keep track of the command
	type and body associated with the command.
	* top.c: Include value.h.  Delete whitespace at the end of lines.
	(build_command_line, get_command_line): New functions.
	(execute_control_command, while_command, if_command): Likewise.
	(realloc_body_list, read_next_line): Likewise.
	(recurse_read_control_structure): Likewise.
	(execute_user_command): Call execute_control_command.
	(read_command_lines): Simplify by calling read_next_line, call
	read_control_structure for "if" and "while" commands.
	(free_command_lines): Free new fields in the command structure.
	(define_command): Reset control_level to zero.
	(init_main): Install command handlers for "if" and "while" commands.