strengthen alignment check for memalign and aligned_alloc

include/mimalloc-internal.h

@@ -232,6 +232,10 @@ static inline size_t _mi_wsize_from_size(size_t size) {
   return (size + sizeof(uintptr_t) - 1) / sizeof(uintptr_t);
 }
 
+// Does malloc satisfy the alignment constraints already?
+static inline bool mi_malloc_satisfies_alignment(size_t alignment, size_t size) {
+  return (alignment == sizeof(void*) || (alignment == MI_MAX_ALIGN_SIZE && size > (MI_MAX_ALIGN_SIZE/2)));
+}
 
 // Overflow detecting multiply
 static inline bool mi_mul_overflow(size_t count, size_t size, size_t* total) {