Small improvements to the indexing in StackAllocator

Signed-off-by: Rick Taylor <rick@tropicalstormsoftware.com>
Start smaller when printf'ing

Signed-off-by: Rick Taylor <rick@tropicalstormsoftware.com>
Templated type for stack allocator indexes

Signed-off-by: Rick Taylor <rick@tropicalstormsoftware.com>
Remove templated index_t for StackAllocator, 2 bytes is optimal.
Halve recorded size, as that allows use to use the full amount for allocations.

Signed-off-by: Rick Taylor <rick@tropicalstormsoftware.com>
Insert free blocks into the free list maintaining order, helps with fragmentation.

Signed-off-by: Rick Taylor <rick@tropicalstormsoftware.com>