Memory provider:
 Remove the get_last_result function and replace it with
 get_last_error. This primary difference is the addition of
 the pError out parameter which returns a native error code
 emitted from a failed provider function which resulted in returning
 UMA_RESULT_ERROR_MEMORY_PROVIDER_SPECIFIC.

Memory_pool:
 Remove the get_last_result function and replace it with
 get_last_allocation_status. For memory pool, I don't think we care
 about a pool-specific error codes. We do, however, want to know why the
 previous allocation/de-allocation failed. Memory pool allocation
 functions only return a pointer so we need an extra function
 (get_last_allocation_status) to get this information.

use get_last_allocation_error to return last error
from allocation functions.

by returning the name directly instead of through out param. This
function is not allowed to fail anyway.

which returns handle to the last failed provider.

This makes error reporting API independent from how
memory pool is using the providers (i.e. whether there is
only a single provider or multiple)