Cannot compile Seq24 using C++11 or newer compilers

[SUK]

I tried to compile Seq24 using newest (2017-08) gcc which failed due to ambiguity between std::mutex (first in C++11) and mutex class in Seq24 project. I'm not sure whenever is this project still active, maybe isn't, so there are two ways to overcome this.
The more correct (yet I was unsuccessfull trying to do this) way is disabling newer C++ features (using -std=c++03), the less correct (but still easy and working) is writing something like
"#define mutex xaxaxaxaxaxa" (without quotes) into src/mutex.h file before "class mutex {" line.