"-X Disables all warnings regardless of use warnings or $^W". See
"perldoc perlrun" or http://perldoc.perl.org/perlrun.html
With the current defaults, warnings are squashed. For example:
$ perl -X -Mwarnings -c -e'BEGIN { 42 + undef }'
-e syntax OK
$ perl -Mwarnings -c -e'BEGIN { 42 + undef }'
Use of uninitialized value in addition (+) at -e line 1.
-e syntax OK
So, it's not clear from the current defaults whether Ale wants to remove
warnings or enable them. As it stands, it's trying to do both and the
disabling appears to win.
This commit enables warnings by default.
