Move expression_context_* globals to parser_state

Move expression_context_* globals to parser_state

This moves the expression_context_block and expression_context_pc
globals to be members of parser_state and updates the parsers.

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

	* rust-exp.y (rust_parser::crate_name, rust_parser::super_name)
	(rust_parser::convert_ast_to_type)
	(rust_parser::convert_ast_to_expression, rust_lex_tests): Update.
	* parser-defs.h (struct parser_state) <parser_state>: Add
	parameters.  Initialize new members.
	<expression_context_block, expression_context_pc>: New members.
	* parse.c (expression_context_block, expression_context_pc):
	Remove globals.
	(parse_exp_in_context): Update.
	* p-exp.y: Update all rules.
	(yylex): Update.
	* m2-exp.y: Update all rules.
	(yylex): Update.
	* go-exp.y (yylex): Update.
	* f-exp.y (yylex): Update.
	* d-exp.y: Update all rules.
	(yylex): Update.
	* c-exp.y: Update all rules.
	(lex_one_token, classify_name, yylex, c_parse): Update.
	* ada-exp.y (write_var_or_type, write_name_assoc): Update.