Some of the flag bits were moved when adding powerpc64 vector support.

Fixes #536

Plus .cfi async unwind info, rearrangement of ffi_call_linux64 and
ffi_call_SYSV function params to avoid register copies, tweaks to
trampolines.

	* src/powerpc/ffitarget.h (FFI_GO_CLOSURES): Define.
	* src/powerpc/ffi.c (ffi_call_int): New function with extra
	closure param, and args rearranged on ffi_call_linux64 and
	ffi_call_SYSV calls, extracted from ..
	(ffi_call): ..here.
	(ffi_call_go, ffi_prep_go_closure): New functions.
	* src/powerpc/ffi_linux64.c (ffi_prep_closure_loc_linux64): Make
	hidden.  Only flush insn part of ELFv2 trampoline.  Don't shuffle
	ELFv1 trampoline.
	(ffi_closure_helper_LINUX64): Replace closure param with cif, fun,
	user_data params.
	* src/powerpc/ffi_powerpc.h (ffi_go_closure_sysv): Declare.
	(ffi_go_closure_linux64): Declare.
	(ffi_call_SYSV, fi_call_LINUX64): Update.
	(ffi_prep_closure_loc_sysv, ffi_prep_closure_loc_linux64): Declare.
	(ffi_closure_helper_SYSV, ffi_closure_helper_LINUX64): Update.
	* src/powerpc/ffi_sysv.c (ASM_NEEDS_REGISTERS): Increase to 6.
	(ffi_prep_closure_loc_sysv): Use bcl in trampoline, put data words
	last, flush just the insn part.
	(ffi_closure_helper_SYSV): Replace closure param with cif, fun and
	user_data params.
	* src/powerpc/linux64.S (ffi_call_LINUX64): Replace hand-written
	.eh_frame with .cfi directives.  Adjust for changed param order.
	Pass extra "closure" param to user function in static chain.  Add
	.cfi directives to describe epilogue.  Don't provide traceback
	table for ELFv2 or _CALL_LINUX.
	* src/powerpc/linux64_closure.S (ffi_closure_LINUX64): Replace
	hand-written .eh_frame with .cfi directives.  Adjust for changed
	ffi_closure_helper_LINUX64 params.  Add .cfi directives to
	describe epilogue.  Don't provide traceback table for ELFv2 or
	_CALL_LINUX.
	(ffi_go_closure_linux64): New function.
	* src/powerpc/sysv.S: Remove redundant .globl ffi_prep_args_SYSV.
	(ffi_call_SYSV): Make hidden.  Replace hand-written .eh_frame with
	.cfi directives.  Adjust for changed params.  Pass extra "closure"
	param to user function in static chain.  Add .cfi directives to
	describe epilogue.
	* src/powerpc/ppc_closure.S (ffi_closure_SYSV): Make hidden.
	Replace hand-written .eh_frame with .cfi directives.  Adjust for
	changed ffi_closure_helper_SYSV params.  Add .cfi directives to
	describe epilogue.  Don't just use nops in the dead __NO_FPRS__
	epilogues.
	(ffi_go_closure_sysv): New function.

code, and makes it possible to link code compiled with different
options to those used to compile libffi.  For example, a
-mlong-double-128 libffi can be used with -mlong-double-64 code.

Using the return value area as a place to pass parameters wasn't such
a good idea, causing a failure of cls_ulonglong.c.  I didn't see this
when running the mainline gcc libffi testsuite because that version of
the test is inferior to the upstreamm libffi test.

Using NUM_FPR_ARG_REGISTERS rather than NUM_FPR_ARG_REGISTERS64 meant
that a parameter save area could be allocated before it was strictly
necessary.  Wrong but harmless.  Found when splitting apart ffi.c
into 32-bit and 64-bit support.

values from 2011-11-12, but in so doing reintroduced string
instructions to sysv.S that are not supported on all powerpc variants.
This patch properly copies the bounce buffer to destination in C code
rather than in asm.

I have tested this on powerpc64-linux, powerpc-linux and
powerpc-freebsd.  Well, the last on powerpc-linux by lying to
configure with

CC="gcc -m32 -msvr4-struct-return -mlong-double-64" \
CXX="g++ -m32 -msvr4-struct-return -mlong-double-64" \
/src/libffi-current/configure --build=powerpc-freebsd

and then

make && make CC="gcc -m32" CXX="g++ -m32" \
RUNTESTFLAGS=--target_board=unix/-m32/-msvr4-struct-return/-mlong-double-64\
 check