[Bug c++/69139] [4.9/5/6 Regression] deduction failure with trailing return type in function template argument

[abutcher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69139

--- Comment #5 from Adam Butcher <abutcher at gcc dot gnu.org> ---
The patch at https://gcc.gnu.org/ml/gcc-patches/2016-02/msg00561.html adds
handling for cv/ref mentioned by TC in #c3.  I've added handling of tx and
exception specs to.