Refactor the lexer/parser to expose friendlier words for scanning tokens. The preferred top-level words now throw an exception on EOF. CREATE -> scan-new CREATE-CLASS -> scan-new-class CREATE-WORD -> scan-new-word CREATE-GENERIC -> scan-new-generic scan -> (scan-token) scan-token now throws on eof (scan-word) returns word/number/f scan-word now throws on eof scan-word-name expects a non-number Fixes #183. Fixes #209.