Remove a bunch of old code and give the static treatment to what's left.

We're no longer using the expansion stack, so its functions can go
along with most of the body of glcpp_parser_lex that was using it.

glcpp.h

@@ -127,16 +127,9 @@ struct glcpp_parser {
 	struct hash_table *defines;
 	string_list_t *active;
 	int space_tokens;
-	expansion_node_t *expansions;
-	int just_printed_separator;
-	int need_newline;
 	skip_node_t *skip_stack;
 };
 
-void
-glcpp_parser_push_expansion_argument (glcpp_parser_t *parser,
-				      int argument_index);
-
 glcpp_parser_t *
 glcpp_parser_create (void);