[PING^2][PATCH] Improve C++ loop's backward-jump location

[Andreas Arnez]

Ping?

  https://gcc.gnu.org/ml/gcc-patches/2015-11/msg01192.html

I guess we want C and C++ behave the same here?

> gcc/cp/ChangeLog:
>  
>       * cp-gimplify.c (genericize_cp_loop): Change LOOP_EXPR's location
>       to start of loop body instead of start of loop.
> 
> gcc/testsuite/ChangeLog:
>  
>       * g++.dg/guality/pr67192.C: New test.