Reorganise bfd/doc/chew.c a little

This also removes some unused variables, and deletes support for the
"var" keyword which isn't used and was broken.  (No means to set
variables, and add_var used push_number inconsistent with its use
elsewhere.)

	* doc/chew.c: Move typedefs before variables, variables before
	functions.
	(die): Move earlier.
	(word_type, sstack, ssp): Delete.
	(dict_type): Delete var field.
	(add_var): Delete.
	(compile): Remove "var" support.