added VARIADIC_SEQ_TO_SEQ

svn path=/trunk/boost/preprocessor/; revision=80704
Updated documentation linking the (v) notation to a named anchor explaining it.

svn path=/trunk/libs/preprocessor/; revision=83890
Updated documentation linking the (v) notation to a named anchor explaining it.

svn path=/trunk/libs/preprocessor/; revision=83891
Removed redundant explanation.

svn path=/trunk/libs/preprocessor/; revision=83898