message: fix optimization in Pointer::isAligned()
diff: @@ -599,7 +599,7 @@ expr Pointer::isAligned(unsigned align) {
  expr blk_align = isBlockAligned(align);
  - if (!observes_addresses() || blk_align.isConst()) {
  + if (!observes_addresses() || (blk_align.isConst() && offset.isConst())) {
  // This is stricter than checking getAddress(), but as addresses are not
  // observed, program shouldn't be able to distinguish this from checking
  // getAddress()
  