Remove warnings under Perl 5.18.

Once I figure out a "preferred" solution for this use case I'll probably
convert to that, until then no reason to pollute with warnings.

I've run a search for other uses of given/when and didn't see any.

kdesrc-build

@@ -74,6 +74,11 @@ use ksb::DependencyResolver 0.20;
 
 use 5.010_000; # Require Perl 5.10.0
 
+# Perl 5.18 warns on given/when/~~, but also is the first version of
+# Perl to support conditional disabling of warnings, so we have to
+# version-protect our warning remover.
+no if $] >= 5.018, 'warnings', 'experimental::smartmatch';
+
 # Make Perl 'plain die' exceptions use Carp::confess instead of their core
 # support. This is not supported by the Perl 5 authors but assuming it works
 # will be better than the alternative backtrace we get (which is to say, none)

modules/ksb/BuildContext.pm

@@ -8,6 +8,7 @@ package ksb::BuildContext;
 use strict;
 use warnings;
 use v5.10;
+no if $] >= 5.018, 'warnings', 'experimental::smartmatch';
 
 our $VERSION = '0.10';
 

modules/ksb/IPC.pm

@@ -8,6 +8,7 @@ package ksb::IPC;
 use strict;
 use warnings;
 use v5.10;
+no if $] >= 5.018, 'warnings', 'experimental::smartmatch';
 
 our $VERSION = '0.20';
 

modules/ksb/Module.pm

@@ -9,6 +9,7 @@ package ksb::Module;
 use strict;
 use warnings;
 use v5.10;
+no if $] >= 5.018, 'warnings', 'experimental::smartmatch';
 
 our $VERSION = '0.10';