BUILD: Fixed C++11 flag

On Clang, activating C++11 is done by setting the flag std=C++11.
On gcc it depends on the version (<= 4.6?).

This is now done.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
BUILD OpenMini standalone now built on Linux

This is still a draft as many things depend on a branch if(UNIX)...

Signed-off-by: Gama <misept.dieseneuf@gmail.com>