deprecation warning P0, P1

[Leopold Toetsch]

Due to adaptions to pdd03 the direct access to the return continuation
is deprecated.

Instead these constructs should be used:

1) PIR code

* return from a sub

.return()
.return(foo)
.return (foo, bar, baz)
...

* get the current continuation (for call/cc)

.include "interpinfo.pasm"
.local pmc cont
cont = interpinfo .INTERPINFO_CURRENT_CONT

The returned continuation is already a real continuation, thus it
doesn't need cloning any more.

* get the current sub

.local pmc sub
sub = interpinfo .INTERPINFO_CURRENT_SUB

2) PASM code

* return from a sub

returncc [ proposed opcode, TBD ]

* get the current continuation / sub

.include "interpinfo.pasm"
interpinfo Px, .INTERPINFO_CURRENT_CONT # or _SUB

leo