[rfc] Fix Obj-C method calls on 64-bit PowerPC

[Joel Brobecker]

> 	* eval.c (evaluate_subexp_standard) [OP_OBJC_MSGCALL]: Support
> 	platforms that use function descriptors.  Prefer to use function
> 	pointer types instead of function types.
> 	* linespec.c (decode_objc): Support function descriptors.  Fully
> 	initialize SAL result.
> 	* objc-lang.c (find_methods): Support function descriptors.
> 	Do not require function symbol to point to text section.
> 
> 	* ppc-sysv-tdep.c (ppc64_sysv_abi_push_dummy_call): When calling
> 	via a function pointer, use the descriptor it point to.
                                                      ^^^^^ points ;-)

Seems fine to me. Given that this fixes SEGVs, we should consider it
for inclusion in the 7.0 branch. You might want to ask ratmice@gmail.com
to give it a test before installing on 7.0, but I don't think it would
buy us much given that you already tested on s390. At least the risk
is limited to ObjC.

-- 
Joel