Ensure megasplat keeps empty trailing fields

The string that a megasplat matched is split on '/'. Without setting an
LIMIT for the split, empty trailing values get stripped. That is;
for the route '/foo/**', the paths '/foo/bar' and '/foo/bar/'
were both giving the splat as [ 'bar' ].

Or, if there were further trailing slashes in the path:
'/foo/bar///a'  gave  ['bar','','','a'] but
'/foo/bar///'   gave  ['bar'].   How's that for inconsistent.

Instead, this commit adds a (negative) limit to the split on megasplat
values so that empty trailing values are kept, which allows you to join
the arrayref of values together and get the original path again. The
above examples are:
'/foo/bar/'     giving ['bar','']
'/foo/bar///a'  giving ['bar','','','a']  #as before
'/foo/bar///'   giving ['bar','','']

This is a subtle change in behaviour, which _may_ cause some Dancers
issues if they are not aware of the change.

Closes #1155.

lib/Dancer2/Core/Route.pm

@@ -112,7 +112,9 @@ sub match {
 
             # megasplat values are split on '/'
             if ($token_or_splat[$i] eq 'megasplat') {
-                $values[$i] = [ split '/' => $values[$i] || '' ];
+                $values[$i] = [
+                    defined $values[$i] ? split( '/' , $values[$i], -1 ) : ''
+                ];
             }
             push @splat, $values[$i];
         }