AIM: factor out aim_memory.h
AIM: use size_t in memory allocation functions

Matches the prototype of malloc.
AIM: add malloc and realloc wrappers

Rounding out the usual memory allocation functions.
AIM: convert uses of AIM_MALLOC/AIM_FREE to aim_malloc/aim_free
AIM: abort on memory allocation failure

Memory allocations will not fail in practice.
AIM: use attribute((malloc))

See http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html
AIM: allow macro override of malloc/calloc/realloc/free
Merge into master from pull request #9:
standardize memory allocation functions (https://github.com/floodlight/infra/pull/9)