Storage at arbitrary address

[athei]

Motivation

I want to place the memory pool at some arbitrary address because my embedded device happens to have some accessible memory there. The embedded static array is too inflexible for that.

Proposed Solution

Adding another constructor to the WeeAlloc struct where I can just pass in pointer + length or a slice and this memory is used no questions asked.

[fitzgen]

I believe that this is basically asking for the same feature as #44 ?

[athei]

Yes I guess its a subset of #44.