[pmc] Clarify dead coroutines

Coros are not resumable when all yield states are exhausted.
This is consistent with the LUA design, which we follow, and all other
coro implementations I know of. Just the parrot book argues that after a
return the state should be automatically reset. Technically no problem, even
without the quirks described in https://github.com/parrot/parrot/issues/564#issuecomment-3503597
or via a seperate reset() method, but semantically an auto-reset is problematic.

Added testcases for all the relevant tickets: #564, #585 and there is on
bug remaining: TT #1003 leading to Null PMC access in get_string on a dead coro
[pmc] Coroutine is now auto-resetting
[pmc] Add Coroutine.reset() method

Mentioned in GH #564.

It is however more efficient to clone an initial coro and
copy this saved clone back, as the context does not need to
be recreated afresh.
coro: implemented autoreset method and attribute

fix crashes in sub_continuation_rewind_environment()
Still using traceflag 8. Maybe I should adopt it or resuse the SUB_CALL_FLAG?
core: autoreset tests, TRACE_CORO, PARROT_TRACE_CORO_STATE_FLAG

add TRACE_CORO define, -t8 only usable when not --optimizing
fix -t2 returning from coroutine msg.
-t2 msg either Coroutine autoreset or Coroutine no autoreset
add autoreset test, not yet working (one-off same as TT #1003)
Document -t8 flag, harmonize parrot usage messages

along parrot and parrot_old
Omit GH issue prefix from ChangeLog if default.
[cage] fix 2 codingstd issues with TRACE_CORO
[core] Disable -t trace flags 4+8 with --optimize

Fixes GH #1105
add to ChangeLog
[test] change closed TT #1003 ticket to new GH #1106
Update steps test to reflect deprecation of parrot_is_shared.
config::auto::pcre: 'unless' block should have been 'if'.

Clean up test files generated during configuration probe.
Avert an uninitialized value warning.

Update one copyright date.
[test] fix t/perl/Parrot_Test.t for VALGRIND

also fix Parrot::Test for valgrind with --pid--, as on darwin
[test] fix t/op/basic.t with -r, and -r error msg

need to use like for -r, as the first pass failed already and
we get "Can't stat t/op/basic_9.pbc, code 2" for the 2nd cmd.
Fixes GH #1107
[docs] Harmonize NAME of Task PMC
native_pbc: generate big-endian 64 bit pbcs for 6.9.0

generated on darwin (linux or bsd is also trivial) with qemu mips64
on a debian image, with gcc-multilib and --cc|ld|link="cc -mabi=64"

See https://people.debian.org/~aurel32/qemu/mips/
qemu-system-mips64 -M malta -kernel vmlinux-2.6.32-5-5kc-malta \
  -hda debian_squeeze_mips_standard.qcow2 \
  -append "root=/dev/sda1 console=tty0" &
login: user; su -; apt-get install gcc-multilib git rsync perl sudo
Supported Release 6.9.0

See the ChangeLog and the end of api.yaml
[build] -mabi=64 for mips/ppc64 with --m=64

Do the right default for --m=64 on ppc/mips with gcc multilib.
These default to 32-bit, and need -mabi=64.
See GH #1110.

tested only on mips64 so far. ppc64 later, arm64 (aarch64) probably
also. sparc64 is different.
[build] --{en,dis}able-static

enable turns off parrot_is_shared, links to static libparrot

disable turns off compiling a static libparrot.a at all.
  the config key libparrot_static is empty then.

See GH #1104