Entirely to TestRubyLexer:
Added lex_state ivar, defaulting to :expr_beg. Now you can set start state before lexing.
Renamed util_* to assert_*
util_lex_token became assert_lex & assert_lex3, now I test lex_state everywhere and optionally test nesting
util_bad_token became refute_lex
Added assert_parse, split from setup_lexer.
moved all assertions up top
[git-p4: depot-paths = "//src/ruby_parser/dev/": change = 8905]