make build pass with GCC < 4.5

[JacksonTian]

Hope to want the commit nodejs/node-v0.x-archive@5926526 merged into io.js。

[rvagg]

the newer V8 we are shipping requires 4.8 at a minimum because they are embracing C++11 features, I'm pretty sure this isn't going to get us anywhere with changing that

[jbergstroem]

I don't think this'll happen either. I guess "unfortunately" should fit in here somewhere, but older distributions should just use a binary package anyway.

[jbergstroem]

Ref #432. We should stick with our previous decision (as our readme.md notes).

[bnoordhuis]

I'm going to close this. g++ 4.8 is the minimum for the reasons outlined above, older versions simply don't support enough of C++11.