add offset==0 condition for fast realloc path in realloc_aligned (issue #1271, issue 6)

Author: daanx

src/alloc-aligned.c

@@ -281,7 +281,7 @@ mi_decl_nodiscard mi_decl_restrict void* mi_calloc_aligned(size_t count, size_t
 
 static void* mi_heap_realloc_zero_aligned_at(mi_heap_t* heap, void* p, size_t newsize, size_t alignment, size_t offset, bool zero) mi_attr_noexcept {
   mi_assert(alignment > 0);
-  if (alignment <= sizeof(uintptr_t)) return _mi_heap_realloc_zero(heap,p,newsize,zero,NULL,NULL);
+  if (alignment <= sizeof(uintptr_t) && offset==0) return _mi_heap_realloc_zero(heap,p,newsize,zero,NULL,NULL);
   if (p == NULL) return mi_heap_malloc_zero_aligned_at(heap,newsize,alignment,offset,zero,NULL);
   size_t size = mi_usable_size(p);
   if (newsize <= size && newsize >= (size - (size / 2))