'spawnw' return value: make it OS-independent

[jkeenan]

This ticket formerly existed as RT #36619. It was entered into RT by particle on 21 Jul 2005. I am moving it to Trac at  the suggestion of whiteknight on his blog, which is also available on  planet.parrotcode (July 17).

Original ticket description:

the return value from 'spawnw' is highly system dependent as currently implemented. instead, 'spawnw' should return something object-like, that wraps the platform-specific semantics.

Here are some files in our distribution that will be relevant to working on this ticket:

config/gen/platform.pm
config/gen/platform/ansi/exec.c
config/gen/platform/generic/exec.c
config/gen/platform/generic/memexec.c
config/gen/platform/openbsd/memexec.c
config/gen/platform/win32/exec.c
src/ops/sys.ops
tools/dev/pbc_to_exe.pir
t/op/spawnw.t
t/pmc/sys.t
docs/book/draft/ch10_opcode_reference.pod
docs/porting_intro.pod

Cf. also TT #847.