Fix use of aligned_alloc() to be ASan-clean.

aligned_alloc() is used by testsc for all its memory allocation, to
avoid false-positive timing variations that depend on memory alignment
rather than actual secret data. But I'd forgotten that aligned_alloc
requires the allocation size to be a multiple of the requested
alignment.

This showed up when I ran testsc in dry-run mode, and my normal build
happened to be using ASan, which complains at the invalid allocation
size. But it was theoretically a problem in all builds of
testsc. (Though, as far as I'm aware, not practically; and it _only_
affected testsc.)

utils/memory.c

@@ -35,7 +35,10 @@ void *safemalloc(size_t factor1, size_t factor2, size_t addend)
 #ifdef MINEFIELD
     p = minefield_c_malloc(size);
 #elif defined ALLOCATION_ALIGNMENT
-    p = aligned_alloc(ALLOCATION_ALIGNMENT, size);
+    /* aligned_alloc requires the allocation size to be rounded up */
+    p = aligned_alloc(
+        ALLOCATION_ALIGNMENT,
+        (size + ALLOCATION_ALIGNMENT - 1) & ~(ALLOCATION_ALIGNMENT-1));
 #else
     p = malloc(size);
 #endif