Non-fatal exceptions

Parrot's exceptions have a 'severity' attribute to indicate, of course, how severe the exception is. The current severities are: (taken from runtime/parrot/include/except_severity.pasm

EXCEPT_NORMAL   
EXCEPT_WARNING  
EXCEPT_ERROR    
EXCEPT_SEVERE   
EXCEPT_FATAL    
EXCEPT_DOOMED   
EXCEPT_EXIT

For a long time now, the spec has said that non-fatal exceptions shouldn't cause termination of the program, but should result in the message being printed and normal execution resuming. This hasn't been the case until today. It was a pretty simple change, but should make some things much nicer in the future.

Here's a simple program demonstrating this behaviour:

.include 'include/except_severity.pasm'
.sub main :main
    say 'before the warning'
    $P0 = new 'Exception'
    $P0['severity'] = .EXCEPT_WARNING
    $P0['message'] = "\tOMG something is kinda wrong"
    throw $P0
    say 'after the warning'
.end

And here's the output:

[sweeks@kweh parrot]$ ./parrot et.pir
before the warning
    OMG something is kinda wrong
after the warning

I've also updated Perl 6's warn() to use a non-fatal exception, meaning that these can now be caught.