Install gcc/g++ 4.7 on Raspberry Pi and set as default

Install gcc-4.7 g++-4.7 on Raspberry Pi, enter the commands:

$ sudo apt-get install gcc-4.7 g++-4.7
$ sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.6 60 --slave /usr/bin/g++ g++ /usr/bin/g++-4.6
$ sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.7 40 --slave /usr/bin/g++ g++ /usr/bin/g++-4.7

Then run the the command and select gcc-4.7.
$ sudo update-alternatives --config gcc