[perl #129430] where-clause on capture does not work

[jn...@jnthn.net via RT]

On Wed Sep 28 03:23:35 2016, gfldex wrote:
> sub f( |c where { c } ) {}; f 42
> 
> # OUTPUT«===SORRY!=== Error while compiling <tmp>␤Variable '&c' is not
> declared␤at <tmp>:1␤------> sub f( |c where { ⏏c } ) {}; f 42␤»
> 
> # expected to work analog to
> 
> sub f( *@a where { @a } ) {}; f 42

The declaration was happening a little too late. Fixed and added a test in 
S12-subset/subtypes.t.

/jnthn