Round out memory pool allocations in fast-import to pointer sizes.

Some architectures (e.g. SPARC) would require that we access pointers
only on pointer-sized alignments.  So ensure the pool allocator
rounds out non-pointer sized allocations to the next pointer so we
don't generate bad memory addresses.  This could have occurred if
we had previously allocated an atom whose string was not a whole
multiple of the pointer size, for example.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

fast-import.c

@@ -342,6 +342,9 @@ static void* pool_alloc(size_t len)
 	}
 
 	r = p->next_free;
+	/* round out to a pointer alignment */
+	if (len & (sizeof(void*) - 1))
+		len += sizeof(void*) - (len & (sizeof(void*) - 1));
 	p->next_free += len;
 	return r;
 }