cxxopts needs less ancient gcc

Ref.: https://github.com/naelstrof/slop/issues/86#issuecomment-328479278

slop.spec.in

@@ -7,7 +7,7 @@ URL:        https://github.com/naelstrof/slop
 License:    GPLv3
 Source0:    __APP_URLBASE__/archive/v%{version}.tar.gz
 
-BuildRequires: gcc-c++
+BuildRequires: gcc-c++ >= 4.9
 BuildRequires: cmake
 BuildRequires: glew-devel
 BuildRequires: glm-devel