SCORE Memory Manager

[Gedare Bloom]

I have an alternate idea that builds on my prior email about memory
protection (Memory Protection (Attributes)). Perhaps RTEMS score could
use a more generic "memory management" implementation. For my
purposes, the score interface would be something like:
* _Memory_Region
  * specifies a base, length, and attribute set
* _Memory_Context
  * set of memory regions
  * could be used for protection or just allocation / traditional memory mgmt

Other score managers might be simplified. For example we might replace
portions of the partition or region managers with new, centralized
score code.  One advantage would be that we could implement
configurable memory protection within the score Memory Handler that
could be used for posix-y protection, optional task stack/heap
isolation, or to enforce new protection libraries as a user API.
Additionally, the code (without protection) could be useful for other
features of memory management. For private heaps we might consider
implementing
_Memory_Arena
  * A memory contexts
  * Custom allocator (custom heap)
Each task could instantiate its own Memory Arena. The score layer
arena could also implement classic API services used by the
region/partition managers.

I think for the time being I will proceed with a distinct "memory
protection manager", but I would like some feedback if anyone thinks
this score memory manager is a good idea or no.

-Gedare