[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
cygwin: check for wrong gcc-4, --disable-shared

replace wrong gcc-4/g++-4 with gcc/g++. GH #1116
set proper libparrot_ldflags for --disable-shared
  (the static lib is in blib/lib)
fix wrong $disable_shared logic in defaults
[gc] decruft -DMEMORY_DEBUG and DETAIL_MEMORY_DEBUG, add -D100

Check -D100 instead of DETAIL_MEMORY_DEBUG when -DMEMORY_DEBUG is enabled.
This way we can run -D101 and -D1 to get verbose and non-verbose GC tracings.

Add new MEMORY_DEBUG_DETAIL_2 macro for fprintf helpers all over.
Move common panic_failed_allocation into gc_private.h, maybe the other
common gc memory funcs also to save space.
Print avail sysmem on startup with -D1.
GH #1108
[core] enable Interp_debug_TEST and flags with flag combinations

Now you can check for multiple flags, e.g.
if (Interp_debug_TEST(interp,
       PARROT_MEM_STAT_DEBUG_FLAG | PARROT_GC_DETAIL_DEBUG_FLAG))
Was used only for single flags, so no changes for existing code.
Document the single flag limitation for the left-over trace_flags test.
There's no -t flag combination, like verbose yet.
[cage] unconst IO_VTABLE * vtables, -Wcast-qual cannot be suppressed

see e.g. https://stackoverflow.com/questions/13249756/explicit-ignore-warning-from-wcast-qual-cast-discards-attribute-const#comment38552597_13253997

2 remaining -Wcast-qual warnings for legacy API.
[gc] check -D1 in startup, add -D2xx MEM_DETAIL_DEBUG_FLAG

Print GS and Memory info on -D1.
Add seperate GC_DEBUG_DETAIL_2 tracer to seperate it from
MEM_DETAIL_DEBUG_FLAG tracing for every single alloc/free.
Document the two new -D100 and -D200 flags with --ccflags=-DMEMORY_DEBUG
[pmc] add Coroutine.mark with caller_seg

Coroutine.mark was just calling Sub.mark and missed to mark
the caller_seg. Do it now properly with inheritance.
Note that this does not fix GH #1109, which is a Coro in a wrong gen
[gc] Better -D1 printout. ChangeLog #1108

$ ulimit -Sv 640
$ ./parrot -D1
Free Memory: 8589934592
Memory via rlimit restricted to: 655360
GC nursery size: 2.0%
GMS GC threshold: 13107
[gc] add trace_pmc_flags_dump

and use it within trace_pmc_dump and #1108, coro in wrong gen
[cage] fixup 2 test errors with pmc flags
[gc] dont stress the GC when tracing the GC

printf directly to stderr in trace_pmc_flags_dump, when not in the debugger
[gc] add missing PackFileView to continuation.mark

also simplify the code a bit
[gc] protect pcc_reuse_continuation from empty data

check for uninitialized continuation->data and allocate fresh then also.
simplify code a bit.
[gc] check empty work_list, optimize gc_gms for -UMEMORY_DEBUG

do not call dummy functions in the common case during GC.

for -DMEMORY_DEBUG only:
protect from empty work_list in check_sanity, which can
occur after the GC was already unblocked.
[gc] new uintval_fmt for size_t printf

memsize is unsigned for >2GB, and we need to print it properly.
otherwise it will print a negative number >4GB in i386
[gc] WIP more GC_DEBUG_DETAIL macros, allow wrong Coros

observe illegal Coros during the GC, Object from wrong generation.

Inline gc_gms_seal_object and gc_gms_unseal_object. They are hot.
[pmc] simplify more mark methods

get the data once, and access the fields directly.
shorter and more cache friendly
[test gc] add real gc stress tests #1108

stress test all GCs, under tight memory --gc-nursery-size=0.0001
and additional --gc-debug runs, with additonal StringBuilder stress via -t
and check the exit codes.
Properly fix SIGNAL detection and error output in Parrot::Test for exit_code_is.
Fails 14/20 tests.

t/harness: add existing TEST_PROG_ARGS to tests single tests, e.g.
  ulimit -Sv 60000
  TEST_PROG_ARGS='--gc-nursery-size=0.05 ' perl t/harness --gc-debug t/pmc/*.t