[Ohrrpgce] SVN: teeemcee/8455 Avoid build errors with gcc 4.9 by setting the correct MOZ_LIBSTDCXX_VER

[subversion at HamsterRepublic.com]

teeemcee
2017-02-26 20:33:38 -0800 (Sun, 26 Feb 2017)
165
Avoid build errors with gcc 4.9 by setting the correct MOZ_LIBSTDCXX_VERSION

I didn't bother to set this variable correctly for gcc versions older than
4.6.1 (2011)
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U   wip/lib/stdc++compat.cpp