Re: [boost] Removing old config macro and increasing compiler requirements.

1. C++03 is exactly as old as Visual Studio 2003 is.

C++03 is also as new as VS2010, and to a lesser extend VS2012 which is the current release of VS and still does not support key C++11 language features. The latest version of MinGW (gcc 4.8.1) for Windows also does not support some of the features mandated by C++11 (mainly library features). The defaults for gcc compilers (and I think clang compilers) is also still C++03 (i.e. the user must specify -std=c++11 to get C++11) I don't know what the state of Intel's compiler is. I don't think dropping C++03 support is warranted at this time, though I do think requiring C++03 minimum compatibility would be ok if it already isn't (especially since C++98 is very similar to C++03).