roxiemem support for packed fixed size allocators
roxiemem support for packed fixed size allocators

packed allocators have the following characteristics
- they are unique to the activityid
- the sizes are 4 byte aligned, not rounded up
- the overhead per row is 4 bytes instead of 8

Cleanup/improve code for memstats function

Signed-off-by: Gavin Halliday <2edfa8aca9fb78974188e5b35be8b52d4e4967ae@lexisnexis.com>

afishbeck/HPCC-Platform,afishbeck/HPCC-Platform,afishbeck/HPCC-Platform,afishbeck/HPCC-Platform,afishbeck/HPCC-Platform,afishbeck/HPCC-Platform