36 - exclude deprecated keywords from tab completion results

[joshsh]

Deprecated keywords, such as "unique" (which superseded by "distinct) are
important for backwards compatibility.  But their continued use should not
be encouraged by their presence in tab completion results (they also tend
to annoy when they force the user to do more work to choose a keyword --
e.g. typing "uni\t" forces a choice between "union" and "unique", whereas
otherwise it would just complete to "union").

Original link: http://code.google.com/p/ripple/issues/detail?id=36