Move innermost_block_tracker global to parse_state

Move innermost_block_tracker global to parse_state

This changes the parsing API so that callers that are interested in
tracking the innermost block must instantiate an
innermost_block_tracker and pass it in.  Then, a pointer to this
object is stored in the parser_state.

2019-04-04  Tom Tromey  <tom@tromey.com>

	* varobj.c (varobj_create): Update.
	* rust-exp.y (struct rust_parser) <update_innermost_block,
	lookup_symbol>: New methods.
	(rust_parser::update_innermost_block, rust_parser::lookup_symbol):
	Rename.
	(rust_parser::rust_lookup_type)
	(rust_parser::convert_ast_to_expression, rust_lex_tests): Update.
	* printcmd.c (display_command, do_one_display): Update.
	* parser-defs.h (struct parser_state) <parser_state>: Add
	"tracker" parameter.
	(block_tracker): New member.
	(class innermost_block_tracker) <innermost_block_tracker>: Add
	"types" parameter.
	<reset>: Remove method.
	(innermost_block): Don't declare.
	(null_post_parser): Update.
	* parse.c (innermost_block): Remove global.
	(write_dollar_variable): Update.
	(parse_exp_1, parse_exp_in_context): Add "tracker" parameter.
	Remove "tracker_types" parameter.
	(parse_expression): Add "tracker" parameter.
	(parse_expression_for_completion): Update.
	(null_post_parser): Add "tracker" parameter.
	* p-exp.y: Update rules.
	* m2-exp.y: Update rules.
	* language.h (struct language_defn) <la_post_parser>: Add
	"tracker" parameter.
	* go-exp.y: Update rules.
	* f-exp.y: Update rules.
	* expression.h (parse_expression, parse_exp_1): Add "tracker"
	parameter.
	* d-exp.y: Update rules.
	* c-exp.y: Update rules.
	* breakpoint.c (set_breakpoint_condition): Create an
	innermost_block_tracker.
	(watch_command_1): Likewise.
	* ada-lang.c (resolve): Add "tracker" parameter.
	(resolve_subexp): Likewise.
	* ada-exp.y (write_var_from_sym): Update.