Fixed undefined behavior in swap and assign.

svn path=/sandbox/boost/incomplete.hpp; revision=367
Small fix to variant::type() for empty-variant case.

svn path=/sandbox/boost/variant.hpp; revision=371
Updated documentation describe empty variant semantics.

svn path=/sandbox/boost/variant.hpp; revision=372
Double-storage strategy used to provide non-empty invariant and strong exception-safety.

svn path=/sandbox/boost/variant.hpp; revision=376
Updated documentation.

svn path=/sandbox/libs/variant/; revision=377
Updated documentation terminology.

svn path=/sandbox/libs/variant/; revision=378
Small changes to variant and related.

svn path=/sandbox/boost/variant.hpp; revision=387
Fixed bug in double-storage-based variant assign.

svn path=/sandbox/boost/variant.hpp; revision=402
Changes to workarounds and to experimental variant< type-sequence > implementation.

svn path=/sandbox/boost/variant.hpp; revision=403
Integrated move semantics with variant assign.

svn path=/sandbox/boost/variant.hpp; revision=407
Integrated move semantics and double-storage technique with variant swap.

svn path=/sandbox/boost/variant.hpp; revision=417
Small fix to variant assign.

svn path=/sandbox/boost/variant.hpp; revision=418
Integrated with move semantics.

svn path=/sandbox/boost/incomplete.hpp; revision=445
Bug fixes and documentation updates.

svn path=/sandbox/boost/incomplete.hpp; revision=697
Variant assignment bug fix.

svn path=/sandbox/boost/variant.hpp; revision=713
Added test for fixed assignment bug.

svn path=/sandbox/libs/variant/; revision=716
MPL preprocessed header workaround.

svn path=/sandbox/libs/variant/; revision=717
1) most of the stuff moved to other .html files
2) New TOC + Introdcution

svn path=/sandbox/libs/variant/; revision=765
.

svn path=/sandbox/libs/variant/; revision=766
Moved one directory up

svn path=/sandbox/libs/variant/; revision=767