* Incorporated Ulf's patches for Booleans
* numbers.h now reimplements real(), imag(), conj() and abs() because C++11 overloads them for doubles but returns complex values in some platforms (OS X)
* I have spent three weeks tracking down why MKL does not work any longer with libtensor on Ubuntu 13.0. Finally found out that the problem is a stupid link strategy that does not link in second-level dependencies. libtensor has been changed to use --no-as-needed to prevent this.