Simplified the reference handling code.
Added object stack manipulation words.
`skip-whitespace` no longer  changes the current file.
Compressed the code a bit. entry_t.exec is now .xt.
Added documentation for the reference words.
Reorganisation: Dissolved section "System variables".
Documented the object stack words.
Added reference variables and object stack words.
Added scope braces to all stream handling words.
Changed names of class words accoring to new naming convention.
Moved scopes such that the command prompt is at object depth 0.

Only then does oclear work.