fix(example) Account for null in allocation size.

[chinoto]

The potential issue won't be seen in the greet example, but could cause issues for those who just copy and paste the code. Perhaps there should be a comment explaining the +1?

Example of issue: Assume two allocations A and B next to each other in memory, where A doesn't account for the null in its size. If A is written first, then B, attempting to read A will result in a concatenation of the two. If B is written first, attempting to read B will result in an empty string.

[chinoto]

While looking through my Javascript port of greet.php I noticed I forgot to include the capacity argument in deallocate (surprisingly caused no errors) and checked the php version, finding that it also didn't account for the null terminator when deallocating.

[Hywan]

Thanks!