[XeTeX] Overfull boxes return status of 0 in XeTeX

[Philip Taylor]

Also please consider the following text from Wikipædia :

> The parent and the child can have an understanding about the meaning
> of the exit statuses. For example, it is common programming practice
> for a child process to return zero to the parent signifying success.
> Apart from this return value from the child, other information like
> how the process exited, either normally or by a signal may also be
> available to the parent process.
> 
> The specific set of codes returned is unique to the program that sets
> it. Typically it indicates success or failure. The value of the code
> returned by the function or program may indicate a specific cause of
> failure. On many systems, the higher the value, the more severe the
> cause of the error.[1] Alternatively, each bit may indicate a
> different condition, which are then ored together to give the final
> value; for example, fsck does this.
> 
> Sometimes, if the codes are designed with this purpose in mind, they
> can be used directly as a branch index upon return to the initiating
> program to avoid additional tests.

** Phil.