Adds a TODO comment in ion_allocation.c / ion_initialize_page_pool.
Adds a TODO comment in ion_allocation.c / ion_initialize_page_pool.

Related to #242
amznlabs/ion-c,amzn/ion-c,amznlabs/ion-c,amzn/ion-c,amzn/ion-c,amznlabs/ion-c,amznlabs/ion-c,amzn/ion-c