more cache manager issues

[Nigel Spon]

>One global `free(arg)' function could then determine the heap
>corresponding to the argument
>by comparing the argument pointer to the standard heap / aligned heap
>starting and end addresses.

I dealt with this by having one heap and an allocator which could return 
aligned blocks by padding the front of the block and returning a pointer 
that was offset 1-3 longwords into the block as necessary. The free 
function then checks for the padding words, which are a value that can't 
appear in a block header. This allows it to locate the real block header 
and free that. 

Not terribly elegant, but it works and has one heap and one free...