sparc: Rewrite everything

It's impossible to call between v8 and v9 ABIs, because of the stack bias
in the v9 ABI.  So let's not pretend it's just not implemented yet.  Split
the v9 code out to a separate file.

The register windows prevent ffi_call from setting up the entire stack
frame the assembly, but we needn't make an indirect call back to prep_args.

src/prep_cif.c

@@ -147,9 +147,6 @@ ffi_status FFI_HIDDEN ffi_prep_cif_core(ffi_cif *cif, ffi_abi abi,
 #if !defined FFI_TARGET_SPECIFIC_STACK_SPACE_ALLOCATION
   /* Make space for the return structure pointer */
   if (cif->rtype->type == FFI_TYPE_STRUCT
-#ifdef SPARC
-      && (cif->abi != FFI_V9 || cif->rtype->size > 32)
-#endif
 #ifdef TILE
       && (cif->rtype->size > 10 * FFI_SIZEOF_ARG)
 #endif
@@ -179,14 +176,6 @@ ffi_status FFI_HIDDEN ffi_prep_cif_core(ffi_cif *cif, ffi_abi abi,
       FFI_ASSERT_VALID_TYPE(*ptr);
 
 #if !defined FFI_TARGET_SPECIFIC_STACK_SPACE_ALLOCATION
-#ifdef SPARC
-      if (((*ptr)->type == FFI_TYPE_STRUCT
-	   && ((*ptr)->size > 16 || cif->abi != FFI_V9))
-	  || ((*ptr)->type == FFI_TYPE_LONGDOUBLE
-	      && cif->abi != FFI_V9))
-	bytes += sizeof(void*);
-      else
-#endif
 	{
 	  /* Add any padding if necessary */
 	  if (((*ptr)->alignment - 1) & bytes)