PHI_FACTOR is a constexpr variable that is defined using std::log.
Though G++ has a constexpr version of std::log, this itself is not spec
complaint (in fact, Clang enforces this). See C++ Spec 26.8 for the
definition of std::log and 17.6.5.6 for the rule regarding adding
constexpr where it isn't specified.
This patch replaces the std::log statement with a version from math.h
that contains the exact value (M_LOG10El).
Signed-off-by: Erich Keane <erich.keane@verizon.net>
Message-Id: <1454603285-32677-1-git-send-email-erich.keane@verizon.net>