printexc: a catch-all exception handler
value f: ('a -> 'b) -> 'a -> 'b
printexc__f fn x applies fn to x and returns the result.
If the evaluation of fn x raises any exception, the
name of the exception is printed on standard error output,
and the programs aborts with exit code 2.
Typical use is printexc__f main (), where main, with type
unit->unit, is the entry point of a standalone program, to catch
and print stray exceptions.
For printexc__f to work properly, the program must have
been linked with the -g option.