[test] fix rounding of benchmarks seconds

some OS have no hires timings on benchmarks.
thus not all floats are printed with a ., esp. on cygwin.
GH #1066.

see http://perl514.cpanel.net/build/builders/parrot-cygwin/builds/41/steps/shell_2/logs/stdio
"0 seconds. 4000 lops/sec"
[test] cannot test stat on cygwin64 GH #1066

skip t/pmc/os.t 10 and 18. failing on cygwin64.
See http://perl514.cpanel.net/build/builders/parrot-cygwin64/builds/42/steps/shell_2/logs/stdio
[test] skip t/codingstd/pod_syntax.t if Capture::Tiny is missing

detected by my cygwin64 smoker, but this is a general problem
ChangeLog: 2 updates to Tests
[test] skip IPv6 socket tests without IPv6, fixes #1068

There are systems without INET6 family support at all. It is a kernel option afterall.
Thanks to basiliscos for reporting
ChangeLog: add GH #1068
Merge branch 'socketipv6-gh1068'

Fix confirmed by user

./parrot t/pmc/socket.t
1..23
ok 1 - Instantiated a Socket PMC
ok 2 - PMC has correct type
ok 3 - can get_fd a Socket
ok 4 - Socket read returns 0 when not connected
ok 5 - Cloned a Socket PMC
ok 6 - Cloned PMC has correct type TT#1820
ok 7 - get_bool on closed Socket
ok 8 - Closed a Socket
ok 9 - A closed Socket returns False
ok 10 - Socket is_closed returned 1 to new socket
ok 11 - Created a TCP Socket
ok 12 - Created a UDP Socket
ok 13 - Socket getprotobyname(icmp) returned 1
ok 14 - Socket getprotobyname(tcp) returned 6
ok 15 - empty protocol name does not coredump
ok 16 - non-existent protocol name does not coredump
ok 17 - Server process started
ok 18 - socket
ok 19 - send
ok 20 - recv
ok 21 - send() big
ok 22 - read(1024) chunked
ok 23 - Exit status of server process
ChangeLog: minor addition benchmarks/run.sh
[test] add t/steps/auto/expect-01.t configure step test
Release 6.3.0 (supported release)

No core or build changes since 6.2.0, just tests and benchmarks
[examples] enable regexdna.pir argv to allow gdb debugging

we now accept an optional filename arg to regexdna.pir
to study GC write barrier crashes with
gdb --args ./parrot examples/shootout/regexdna.pir examples/shootout/regexdna.pir_input
pmc2c: inline gc write barrier into vtable methods

removed wrong UNUSED(INTERP) and UNUSED(SELF)
some methods with return values are marked TODO, need to add the write barriers manually.

A missing write barrier caused one error:
t/examples/shootout.t: 16 examples/shootout/regexdna.pir SEGV

TODO GC write barrier to:
default.pop_float
default.pop_integer
default.pop_pmc
default.pop_string
default.shift_float
default.shift_integer
default.shift_pmc
default.shift_string
CallContext.shift_pmc
CallContext.shift_string
Key.shift_pmc
ArrayIterator.pop_float
ArrayIterator.pop_integer
ArrayIterator.pop_pmc
ArrayIterator.pop_string
ArrayIterator.shift_float
ArrayIterator.shift_integer
ArrayIterator.shift_pmc
ArrayIterator.shift_string
Task.pop_pmc
Capture.pop_float
Capture.pop_integer
Capture.pop_pmc
Capture.pop_string
Capture.shift_float
Capture.shift_integer
Capture.shift_pmc
Capture.shift_string
HashIterator.shift_integer
HashIterator.shift_pmc
HashIterator.shift_string
ImageIOThaw.shift_float
ImageIOThaw.shift_integer
ImageIOThaw.shift_pmc
ImageIOThaw.shift_string
ResizablePMCArray.pop_float
ResizablePMCArray.pop_integer
ResizablePMCArray.pop_pmc
ResizablePMCArray.pop_string
ResizablePMCArray.shift_float
ResizablePMCArray.shift_integer
ResizablePMCArray.shift_pmc
ResizablePMCArray.shift_string
Object.pop_float
Object.pop_integer
Object.pop_pmc
Object.pop_string
Object.shift_float
Object.shift_integer
Object.shift_pmc
Object.shift_string
OrderedHashIterator.pop_pmc
OrderedHashIterator.shift_pmc
OrderedHashIterator.shift_string
PMCList.pop_pmc
PMCList.shift_pmc
ResizableBooleanArray.pop_integer
ResizableBooleanArray.shift_integer
ResizableFloatArray.pop_float
ResizableFloatArray.shift_float
ResizableIntegerArray.pop_integer
ResizableIntegerArray.shift_integer
ResizableStringArray.pop_float
ResizableStringArray.pop_integer
ResizableStringArray.pop_pmc
ResizableStringArray.pop_string
ResizableStringArray.shift_float
ResizableStringArray.shift_integer
ResizableStringArray.shift_pmc
ResizableStringArray.shift_string
Scheduler.shift_pmc
StringIterator.pop_integer
StringIterator.pop_pmc
StringIterator.pop_string
StringIterator.shift_integer
StringIterator.shift_pmc
StringIterator.shift_string
[pmc2c] WIP :no_wb, detection of :manual_wb, RETURN() also for VTABLE methods

add_write_barrier now calls Parrot::Pmc2c::PCCMETHOD::rewrite_RETURNs, but
this does not work yet.
[pmc] partially use new WB markers
[pmc2c] set manual_wb for :no_wb and PARROT_GC_WRITE_BARRIER in --dump

detect it now earlier, in the parser
[pmc2c] small decl optimization