[Bug testsuite/57301] bit rotation is optimized in c but not c++

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57301

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
This regressed presumably with r131862 .  Anyway, I don't think the rotate
detection improvements should be backported to the release branches, therefore
this will need to be FIXED in 4.9+ only.