Cleaned up macros for virtual memory allocation
Cleaned up macros for virtual memory allocation

Added LTALLOC_VMSIZE. It's optional, if LTALLOC_HAS_VMSIZE is not 1, large allocations sizes are stored in a ptrie.
Added LTALLOC_VMALLOC_ALIGNED. Optional as well, if not defined it's implemented based on VMALLOC (like before).

r-lyeh/ltalloc,r-lyeh/ltalloc