limit aligned allocation to power-of-two alignment

src/alloc-posix.c

@@ -71,7 +71,8 @@ void* mi_pvalloc(size_t size) mi_attr_noexcept {
 }
 
 void* mi_aligned_alloc(size_t alignment, size_t size) mi_attr_noexcept {
-  if (alignment != 0 && (size%alignment) != 0) return NULL; // C11 required; <https://en.cppreference.com/w/c/memory/aligned_alloc>
+  if (alignment==0 || !_mi_is_power_of_two(alignment)) return NULL; 
+  if ((size&(alignment-1)) != 0) return NULL; // C11 requires integral multiple, see <https://en.cppreference.com/w/c/memory/aligned_alloc>
   return mi_malloc_aligned(size, alignment);
 }