[Bug c++/23975] do not optimize for a 'const double'

[lidaobing at gmail dot com]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|                            |4.1.0
      Known to work|                            |2.95.4 3.3.5 3.4.5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23975