Integrate perlio:

[ 16809]
Add IO::Scalar fail case to the tests.

[ 16808]
Fix for the IO::Scalar bug (I think).
At tie time break the loop but in a different place:
A. Increment REFCNT of the RV involved in the self-tie
B. Decrement REFCNT of the thing RV points to (e.g. the GV)
At mg_free time
Break the connection between the RV and its referent
so that we do not try and free it (again).

[ 16805]
**** UNSAFE **** partial fix for IO::Scalar and local ties.
Only op/local.t fails but it is nasty... try valgrind on other machine.
p4raw-link: @16809 on //depot/perlio: 6751fbc4613da48d58726f127239e6f792ac8c57
p4raw-link: @16808 on //depot/perlio: 3977871ddaef13bab4556a4c080d3871df7b231f
p4raw-link: @16805 on //depot/perlio: 2628be26342842a5f886163d0568170afde998a0

p4raw-id: //depot/perl@16810