CMakeLists.txt: require C++11 support, disable SSE/SSE2 if no C++11
lfExtModifier::ModifyColor_DeVignetting_PA_Select: add SSE2 postfix
lfExtModifier::ModifyColor_DeVignetting_PA_SSE2: reduce code duplication
This de-duplicates almost half of the lines in that file.
[WIP] lfExtModifier::ModifyColor_DeVignetting_PA_: add SSE for lf_f32