Added debugging info to RubyLexer#advance when yylex returns nil.
Removed RubyLexer#expr_beg_push.
Removed RubyLexer#fix_arg_lex_state.
Added RubyLexer#result, refactoring a common pattern.
Added RubyLexer#expr_result (a morph of expr_beg_push).
Added RubyLexer#arg_state (a non-mutative morph of fix_arg_lex_state).
Replaced every section I could with calls to result.
RubyLexer#yylex went from 639 lines to 502! Oddly... flog went up by 64.6. :(

[git-p4: depot-paths = "//src/ruby_parser/dev/": change = 8870]