vppinfra: store vector header size and alignment into header

vppinfra: store vector header size and alignment into header

On the forst vector alloc values are stored into header.
Later, when vector grows values from header are used istead of provided
ones.

In the debug image code will assert if same values are not provided.

Type: improvement
Change-Id: I8fdcfa495e9c1df0f6392c90f634e8c74b73b328
Signed-off-by: Damjan Marion <damarion@cisco.com>