cpp/named req/AllocatorAwareContainer

A AllocatorAwareContainer is a Template:concept that has some extra requirements derived from its use of an allocator object.

Legend
`X`	Container type
`T`	Element type
`A`	Allocator for `T`
`a`, `b`	Objects of type `X` (non-const lvalue)
`t`	Object of type `T` (lvalue or const rvalue)
`rv`	Object of type `T` (non-const rvalue)
`m`	Object of type `A`
`Q`	Allocator type

expression	return type	pre/requirements	post/effects	complexity
allocator_type	`A`	allocator_type::value_type must be the same as X::value_type		constant
get_allocator()	`A`			constant
X u;			u.empty() == true && u.get_allocator() == A()	constant
X u(m);			u.empty() == true && u.get_allocator() == m	constant
X u(t,m);			u == t && u.get_allocator() == m	linear
X u(rv);		Move constructor of `A` must not throw exceptions	`u` has the same elements and an equal allocator as `rv` had before the construction	constant
X u(rv,m);			The elements of `u` are the same or copies of those of `rv` and u.get_allocator() == m	constant if m == rv.get_allocator(), otherwise linear
a = t	X&		a == t	linear
a = rv	X&		All existing elements of `a` are either move assigned to or destroyed	linear
a.swap(b)	void		Exchanges the contents of `a` and `b`	constant