[build] fix powerpc --m=64 GH #1110

ppc64 can run on powerpc 32bit OS with a ppc64 CPU, and needs -m64 then.
-mabi=64 does not work there.
[test] fix threads_io.t on pure redhat/centos

perl Time::HiRes is not installed there on a fresh system.
See http://smolder.parrot.org/app/projects/tap_stream/45422/267
Can't locate Time/HiRes.pm in @INC at t/src/threads_io.t line 10.
s/ /_/ for key in extra data sent to Smolder. Fixes GH#1078
[test] more smolder fixes for bad YAML::Tiny versions

It started failing around YAML::Tiny 1.59.
Now replace all spaces with '_' to work even with
newer YAML::Tiny versions.
Fixes GH #1078
[test] change comment about #1078 and #1040
ChangeLog entry for smolder #1078
[imcc] document .lex "" limitation. add -d2 for MKCONST

Handle GH #1095 .lex corner cases with double-quotes.
Do not use it until refactored.

Add a new -d2 flag to print mk_const strings, useful to find
about quoting and escaping, or not. Was used for LEXER some years ago.
[test] todo .lex "" testcase GH #1095
darwin --m=32: fix Parrot_sysmem_amount GH #1113

Need to use HW_PHYSMEM there. No chance to get >2GB RAM in i386.
This syscall worked on darwin/ppc32 also before.
Avoid backtrace within an sysmem exception GH #1113

Protect too early exception call via Parrot_default_encoding_ptr check.
This should be calling PANIC, but we do not want to dump core here.
sysctl err msg and location should be enough.
[docs] improve some internal GC pods
[GH #935] honor user-rlimits for returned sysmem_amount (untested)

We need to check for RLIMIT_DATA and then RLIMIT_AS,
first hard, then soft limits.
[GH #935] add t/stress/gc.t

use from cmd-line as ./parrot t/stress/gc_2.pir 1000000
ulimit -Sv 64000
./parrot t/stress/gc_3.pir 1000000
ulimit -Sv unlimited
honor rlimit on darwin also (just RSS, not AS) GH #935

With this change and ulimit -v 640 the GC bugs are easily
reproduced now also on darwin.
Merge branch 'smoke-me/rlimit-gh935'
ChangeLog: stronger #1095 line
ChangeLog: actually fixed make smoke, now stable
[tools] Fix windows pbc_to_exe, missing unistd.h GH #1114

Thanks to FROGGS for the failure report.
[tools] fixup pbc_to_exe fix, missing unistd.h with --optimize

PARROT_HAS_HEADER_UNISTD is only defined after loading parrot/api.h
Fixes #1117
[tools] more pbc_to_exe fixup for unistd.h with --optimize

Only _WIN32 has no unistd.h. Should close #1117