newsbeuter 2.7 - fix compilation with libc++

Newsbeuter uses the tr1 namespace for C++11 functionality. This breaks
compilation on OS X >= 10.9, as libstdc++ has been replaced by libc++.
The patch that is added to the formula removes the tr1 namespace and
fixed compilations with libc++.

The developer is aware of the problem:
https://github.com/akrennmair/newsbeuter/issues/108
There exists a c++11 branch of newsbeuter, however for the time being it
is not going to be merged into the main release to retain compatibility
with systems that have no native C++11 support (yet).