Add documentation for collections.deque().

Doc/lib/lib.tex

@@ -125,6 +125,7 @@ and how to embed it in other applications.
 \input{librandom}
 \input{libwhrandom}
 \input{libbisect}
+\input{libcollections}
 \input{libheapq}
 \input{libarray}
 \input{libsets}