tlsf_memalign_offs() function

Allocate memory of at least `size` bytes where byte at `data_offset` will be aligned to `alignment`. This function will allocate memory pointed by `ptr`. However, the byte at `data_offset` of this piece of memory (i.e., byte at `ptr` + `data_offset`) will be aligned to `alignment`. This function is useful for allocating memory that will internally have a header, and the usable memory following the header (i.e. `ptr` + `data_offset`) must be aligned. For example, a call to `multi_heap_aligned_alloc_impl_offs(heap, 64, 256, 20)` will return a pointer `ptr` to free memory of minimum 64 bytes, where `ptr + 20` is aligned on `256`. So `(ptr + 20) % 256` equals 0.