[crypt.pl] introduce X::Hanoi type

Now all the hanoi-related exceptions inherit from it.
moritz++ for suggestion.

crypt.pl

@@ -32,7 +32,10 @@
     has $.target;
 }
 
-class X::Hanoi::LargerOnSmaller is Exception {
+class X::Hanoi is Exception {
+}
+
+class X::Hanoi::LargerOnSmaller is X::Hanoi {
     has $.larger;
     has $.smaller;
 
@@ -41,7 +44,7 @@
     }
 }
 
-class X::Hanoi::NoSuchRod is Exception {
+class X::Hanoi::NoSuchRod is X::Hanoi {
     has $.rod;
     has $.name;
 
@@ -50,15 +53,15 @@
     }
 }
 
-class X::Hanoi::RodHasNoDisks is Exception {
+class X::Hanoi::RodHasNoDisks is X::Hanoi {
     has $.name;
 
     method message($_:) {
         "Cannot move from the {.name} rod because there is no disk there"
     }
 }
 
-class X::Hanoi::CoveredDisk is Exception {
+class X::Hanoi::CoveredDisk is X::Hanoi {
     has $.disk;
     has @.covered_by;
 
@@ -73,15 +76,15 @@
     }
 }
 
-class X::Hanoi::ForbiddenDiskRemoval is Exception {
+class X::Hanoi::ForbiddenDiskRemoval is X::Hanoi {
     has $.disk;
 
     method message($_:) {
         "Removing the {.disk} is forbidden"
     }
 }
 
-class X::Hanoi::DiskHasBeenRemoved is Exception {
+class X::Hanoi::DiskHasBeenRemoved is X::Hanoi {
     has $.disk;
     has $.action;
 
@@ -90,15 +93,15 @@
     }
 }
 
-class X::Hanoi::NoSuchDisk is Exception {
+class X::Hanoi::NoSuchDisk is X::Hanoi {
     has $.disk;
 
     method message($_:) {
         "Cannot add a {.disk} because there is no such disk"
     }
 }
 
-class X::Hanoi::DiskAlreadyOnARod is Exception {
+class X::Hanoi::DiskAlreadyOnARod is X::Hanoi {
     has $.disk;
 
     method message($_:) {