Streamline exit call syntax

[hakre]

After review of patches in #15518 it came to my attention that exit is sometimes called with and sometime w/o paranthesis.

As #15518 makes use of the exit; variant, all occurences of exit(); can be replaced with it.

break; after exit; is useless, let me know if that can be removed or should be still in because of code consistency (e.g. switch cases code formatting always ending in break).

break;'s should stay.

I think I slightly prefer exit() over exit.

Whatever - Future Release.

I think it's a good idea to remove the parentheses on language constructs like this and include_once, so as to remind folks that they're not truly functions and will behave somewhat differently.

And the parentheses take up unnecessary file size. :-)