(1) Comment about incomplete<T> employing heap-allocation for T values

(2) operator<< added to the synopsis
(3) not-a-reference requirement added to BoundedType specification


[SVN r19342]

libs/variant

@@ -1 +1 @@
-Subproject commit 47d9df4581f00b7410d84fe055e42b2006438ace
+Subproject commit 1645655ae211f96da3c56ce547f2657eade533d4