ntdll: Add RtlRestoreContext implementation

[Sebastian Lackner]

On 04.07.2016 10:55, Piotr Caban wrote:
> Signed-off-by: Piotr Caban <piotr at codeweavers.com>
> ---
>  dlls/kernel32/kernel32.spec |  2 +-
>  dlls/ntdll/ntdll.spec       |  1 +
>  dlls/ntdll/signal_x86_64.c  | 73 +++++++++++++++++++++++++--------------------
>  3 files changed, 42 insertions(+), 34 deletions(-)
> 

Your patch also changes unwinding behavior in case of MSVCRT_JUMP_BUFFER.
Previously the instruction pointer stored in the jump buffer was ignored,
now it will overwrite the value passed as target_ip. Is that intentional?