RTXI is now compiled using flags -O3 and -std=c++11.
C++11 requires <unistd.h> includes for ni_device source files.
Atomic FIFO implementation added.
Data recorder now uses lock free atomic FIFO to greatly improve performance.

Added boost check to configure and corresponding m4 script.
Compiling with C++11 requires libboost version > 1.54 due to bugs in old version of the library.