tccgen.c: Use memmove for struct assignment: dest and src may be equal.

tccgen.c

@@ -2576,7 +2576,8 @@ ST_FUNC void vstore(void)
                 vpush_global_sym(&func_old_type, TOK_memcpy4);
             else
 #endif
-            vpush_global_sym(&func_old_type, TOK_memcpy);
+            /* Use memmove, rather than memcpy, as dest and src may be same: */
+            vpush_global_sym(&func_old_type, TOK_memmove);
 
             vswap();
             /* source */