Move lexptr and prev_lexptr to parser_state

Move lexptr and prev_lexptr to parser_state

This removes the lexptr and prev_lexptr globals, in favor of members
of parser_state.  prev_lexptr could be isolated to each parser, but
since every parser uses it, that did not seem necessary.

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

	* rust-exp.y (struct rust_parser) <lex_hex, lex_escape,
	lex_operator, push_back>: New methods.
	Update all rules.
	(rust_parser::lex_hex, lex_escape): Rename and update.
	(rust_parser::lex_string, rust_parser::lex_identifier): Update.
	(rust_parser::lex_operator): Rename and update.
	(rust_parser::lex_number, rustyylex, rustyyerror)
	(rust_lex_test_init, rust_lex_test_sequence)
	(rust_lex_test_push_back, rust_lex_tests): Update.
	* parser-defs.h (struct parser_state) <parser_state>: Add "input"
	parameter.
	<lexptr, prev_lexptr>: New members.
	(lexptr, prev_lexptr): Don't declare.
	* parse.c (lexptr, prev_lexptr): Remove globals.
	(parse_exp_in_context): Update.
	* p-exp.y (yylex, yyerror): Update.
	* m2-exp.y (parse_number, yylex, yyerror): Update.
	* go-exp.y (lex_one_token, yyerror): Update.
	* f-exp.y (match_string_literal, yylex, yyerror): Update.
	* d-exp.y (lex_one_token, yyerror): Update.
	* c-exp.y (scan_macro_expansion, finished_macro_expansion)
	(lex_one_token, yyerror): Update.
	* ada-lex.l (YY_INPUT): Update.
	(rewind_to_char): Update.
	* ada-exp.y (yyerror): Update.