[Bug libstdc++/60970] Support std::hash with enum types (LWG 2148)

[ville.voutilainen at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60970

--- Comment #3 from Ville Voutilainen <ville.voutilainen at gmail dot com> ---
Patch available: https://gcc.gnu.org/ml/gcc-patches/2015-07/msg02162.html