gnu/154385: Minor fixes to contrib/libstdc++

[Pedro F. Giffuni]

I think I've cleared the mistery of the libstdc++ license:

According to the FSF, the library for libstdc++ is GPL3 plus runtime exception:
http://gcc.gnu.org/onlinedocs/libstdc++/manual/license.html

However, this license is dated Version 3.1, 31 March 2009 but the latest libstdc++ for the 4.2-branch was released 2008-05-19.

The license in the libstdc++ and the parent directory hasn't changed and appears to be LGPL version 2.1.
http://gcc.gnu.org/viewcvs/branches/gcc-4_2-branch/

I would think that we can update libstdc++ to the latest version in the gcc-4_2 branch (GCC 4.2.4), which has many fixes for boost, etc.

Feel free to close this PR and consider updating libstdc++ by regular means.