Issue with c++11 support

[Nicolas Pavillon]

Hello, 

When trying to upgrade akonadi, I realised that it fails on 10.8 and earlier, as it seems to require in the latest versions a full c++11 support, so that it fails with errors of the type:
/opt/local/var/macports/build/_opt_mports_dports_devel_akonadi/akonadi/work/akonadi-1.13.0/server/tests/unittest/akappendhandlertest.cpp:523:26: error: no matching constructor for initialization of 'const std::vector<TagHelper> &'
        updateTags(tags, { { QLatin1String("PLAIN"), utf8String } });
As trying to force the build with -stdlib=libc++ would provide libraries with issues on runtime, I am not sure of what could be done, as there is apparently no switch in the code to use older syntaxes. 

One possibility would be to make an additional port akonadi112 that older systems could rely on, but this seems quite a hassle. I am missing something that could tackle the issue?

Cheers, 

Nicolas