I had similar problems compiling my c++11 code on government supercomputers that refused to update the GCC compilers because of the infamous red tape that anyone who works in the government knows all too well. So I had to compile the latest GCC in my local working directory and just set the proper environment variables before compiling my own code.
Good news is that it isn't too difficult, if no one can help you by tomorrow then I can definitely help you out since it is too late in the evening here.
EDIT:--------------
Actually found some notes I left someone else for compiling GCC locally. Might be of some use...
You need:
gmp
mpc
mpfr
Just stick those unzipped directories in your gcc-source (in my case it was "gcc-svn", yours might be "gcc-4.8.1") directory.
Then go back a directory and make a directory called "gcc-build".
Go inside gcc-build and type the command below replacing it with your directory structure (note --- prefix will be the directory it installs all the goodies like bin and lib64):
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../gcc-svn/./configure --prefix=/home/nickjer/gcc --with-mpfr-include=/home/nickjer/gcc-build/../gcc-svn/mpfr/src --with-mpfr-lib=/home/nickjer/gcc-build/mpfr/src/.libs --disable-multilib
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Then type "gmake -j <# cpu cores>" and go eat dinner.
Then "gmake install".
I wrote that for gcc-4.7.2, so might need some tweaking. Also, you can remove the --prefix parameter if you want to install it globally. You will need to be root or use sudo for that when you make install it.
